feat(wallet): scaffold wallet module structure

Task 1 of Phase 1 - Module Scaffolding

- Created features/wallet/api module with WalletEntryPoint and WalletState
- Created features/wallet/impl module with Metro DI setup
- Created features/wallet/test module with FakeWalletEntryPoint
- Added PaymentFlowNode placeholder with Appyx navigation
- Added Cardano client library dependencies (0.7.1)
- Added proguard rules for Cardano library
- Added basic unit tests for WalletState

The module follows Element X patterns:
- Metro for dependency injection (@ContributesTo, @ContributesBinding, @ContributesNode)
- Appyx for navigation (BaseFlowNode pattern)
- api/impl/test module separation
- Feature entry point pattern for navigation

This module scaffolding blocks all subsequent tasks (2-8) in Phase 1.

features/wallet/impl/src/main/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (c) 2026 Sulkta Coop.
+  ~
+  ~ SPDX-License-Identifier: AGPL-3.0-only
+  -->
+<manifest />

features/wallet/impl/src/main/kotlin/io/element/android/features/wallet/impl/DefaultWalletEntryPoint.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2026 Sulkta Coop.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package io.element.android.features.wallet.impl
+
+import com.bumble.appyx.core.modality.BuildContext
+import com.bumble.appyx.core.node.Node
+import dev.zacsweers.metro.ContributesBinding
+import io.element.android.features.wallet.api.WalletEntryPoint
+import io.element.android.libraries.architecture.createNode
+import io.element.android.libraries.di.SessionScope
+import io.element.android.libraries.matrix.api.core.RoomId
+import io.element.android.libraries.matrix.api.core.UserId
+import javax.inject.Inject
+
+@ContributesBinding(SessionScope::class)
+class DefaultWalletEntryPoint @Inject constructor() : WalletEntryPoint {
+    class Builder(
+        private val parentNode: Node,
+        private val buildContext: BuildContext,
+        private val callback: WalletEntryPoint.Callback,
+    ) : WalletEntryPoint.Builder {
+        private var roomId: RoomId? = null
+        private var recipientUserId: UserId? = null
+        private var recipientAddress: String? = null
+        private var amount: String? = null
+
+        override fun setRoomId(roomId: RoomId): Builder {
+            this.roomId = roomId
+            return this
+        }
+
+        override fun setRecipientUserId(userId: UserId?): Builder {
+            this.recipientUserId = userId
+            return this
+        }
+
+        override fun setRecipientAddress(address: String?): Builder {
+            this.recipientAddress = address
+            return this
+        }
+
+        override fun setAmount(amount: String?): Builder {
+            this.amount = amount
+            return this
+        }
+
+        override fun build(): Node {
+            val inputs = PaymentFlowNode.Inputs(
+                roomId = requireNotNull(roomId) { "roomId must be set" },
+                recipientUserId = recipientUserId,
+                recipientAddress = recipientAddress,
+                amount = amount,
+            )
+            return parentNode.createNode<PaymentFlowNode>(buildContext, listOf(inputs, callback))
+        }
+    }
+
+    override fun paymentFlowBuilder(
+        parentNode: Node,
+        buildContext: BuildContext,
+        callback: WalletEntryPoint.Callback,
+    ): WalletEntryPoint.Builder {
+        return Builder(parentNode, buildContext, callback)
+    }
+}

features/wallet/impl/src/main/kotlin/io/element/android/features/wallet/impl/PaymentFlowNode.kt

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+/*
+ * Copyright (c) 2026 Sulkta Coop.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package io.element.android.features.wallet.impl
+
+import android.os.Parcelable
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import com.bumble.appyx.core.modality.BuildContext
+import com.bumble.appyx.core.node.Node
+import com.bumble.appyx.core.plugin.Plugin
+import com.bumble.appyx.navmodel.backstack.BackStack
+import dev.zacsweers.metro.Assisted
+import dev.zacsweers.metro.AssistedInject
+import io.element.android.annotations.ContributesNode
+import io.element.android.features.wallet.api.WalletEntryPoint
+import io.element.android.libraries.architecture.BackstackView
+import io.element.android.libraries.architecture.BaseFlowNode
+import io.element.android.libraries.architecture.NodeInputs
+import io.element.android.libraries.architecture.callback
+import io.element.android.libraries.architecture.createNode
+import io.element.android.libraries.di.SessionScope
+import io.element.android.libraries.matrix.api.core.RoomId
+import io.element.android.libraries.matrix.api.core.UserId
+import kotlinx.parcelize.Parcelize
+
+@ContributesNode(SessionScope::class)
+@AssistedInject
+class PaymentFlowNode(
+    @Assisted buildContext: BuildContext,
+    @Assisted plugins: List<Plugin>,
+) : BaseFlowNode<PaymentFlowNode.NavTarget>(
+    backstack = BackStack(
+        initialElement = NavTarget.Confirm,
+        savedStateMap = buildContext.savedStateMap,
+    ),
+    buildContext = buildContext,
+    plugins = plugins
+) {
+    @Parcelize
+    data class Inputs(
+        val roomId: RoomId,
+        val recipientUserId: UserId?,
+        val recipientAddress: String?,
+        val amount: String?,
+    ) : NodeInputs, Parcelable
+
+    private val callback: WalletEntryPoint.Callback = callback()
+    private val inputs: Inputs = plugins.filterIsInstance<Inputs>().first()
+
+    sealed interface NavTarget : Parcelable {
+        @Parcelize
+        data object Confirm : NavTarget
+
+        @Parcelize
+        data object Success : NavTarget
+    }
+
+    override fun resolve(navTarget: NavTarget, buildContext: BuildContext): Node {
+        return when (navTarget) {
+            NavTarget.Confirm -> {
+                // TODO: Implement PaymentConfirmNode
+                createNode<PlaceholderNode>(buildContext, listOf(PlaceholderNode.Inputs("Payment Confirm")))
+            }
+            NavTarget.Success -> {
+                // TODO: Implement PaymentSuccessNode
+                createNode<PlaceholderNode>(buildContext, listOf(PlaceholderNode.Inputs("Payment Success")))
+            }
+        }
+    }
+
+    @Composable
+    override fun View(modifier: Modifier) {
+        BackstackView()
+    }
+}
+
+/**
+ * Placeholder node for development. Will be replaced with actual implementations.
+ */
+@ContributesNode(SessionScope::class)
+@AssistedInject
+class PlaceholderNode(
+    @Assisted buildContext: BuildContext,
+    @Assisted plugins: List<Plugin>,
+) : Node(buildContext, plugins = plugins) {
+    @Parcelize
+    data class Inputs(val label: String) : NodeInputs, Parcelable
+
+    private val inputs: Inputs = plugins.filterIsInstance<Inputs>().first()
+
+    @Composable
+    override fun View(modifier: Modifier) {
+        Box(
+            modifier = modifier.fillMaxSize(),
+            contentAlignment = Alignment.Center,
+        ) {
+            Text(text = "Placeholder: ${inputs.label}")
+        }
+    }
+}

features/wallet/impl/src/main/kotlin/io/element/android/features/wallet/impl/di/WalletModule.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2026 Sulkta Coop.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package io.element.android.features.wallet.impl.di
+
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.ContributesTo
+import dev.zacsweers.metro.ObjectFactory
+import dev.zacsweers.metro.Provides
+import dev.zacsweers.metro.SingleIn
+import kotlinx.serialization.json.Json
+
+/**
+ * DI module providing wallet-related dependencies.
+ */
+@ContributesTo(AppScope::class)
+@ObjectFactory
+interface WalletModule {
+    companion object {
+        @Provides
+        @SingleIn(AppScope::class)
+        fun provideWalletJson(): Json = Json {
+            ignoreUnknownKeys = true
+            isLenient = true
+            encodeDefaults = true
+        }
+    }
+}

features/wallet/impl/src/test/kotlin/io/element/android/features/wallet/impl/WalletStateTest.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2026 Sulkta Coop.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package io.element.android.features.wallet.impl
+
+import com.google.common.truth.Truth.assertThat
+import io.element.android.features.wallet.api.WalletState
+import org.junit.Test
+
+class WalletStateTest {
+    @Test
+    fun `initial state has correct defaults`() {
+        val state = WalletState.Initial
+
+        assertThat(state.hasWallet).isFalse()
+        assertThat(state.address).isNull()
+        assertThat(state.balanceLovelace).isNull()
+        assertThat(state.balanceAda).isNull()
+        assertThat(state.isLoading).isTrue()
+        assertThat(state.error).isNull()
+    }
+
+    @Test
+    fun `state can be updated`() {
+        val state = WalletState(
+            hasWallet = true,
+            address = "addr1test",
+            balanceLovelace = 10_000_000L,
+            balanceAda = "10",
+            isLoading = false,
+            error = null,
+        )
+
+        assertThat(state.hasWallet).isTrue()
+        assertThat(state.address).isEqualTo("addr1test")
+        assertThat(state.balanceLovelace).isEqualTo(10_000_000L)
+        assertThat(state.balanceAda).isEqualTo("10")
+        assertThat(state.isLoading).isFalse()
+    }
+}