feat(wallet): NFT thumbnails and metadata display in Assets tab

- Add NFT metadata fetching via Koios asset_info endpoint
- Parse CIP-25 onchain_metadata for image, name, description
- Convert IPFS URLs to ipfs.io gateway URLs
- Display 64dp thumbnails with 8dp rounded corners using Coil AsyncImage
- Add bottom sheet detail view for NFT expansion (larger image + metadata)
- Graceful fallback with placeholder icons on image load failure
- Load metadata in presenter, cache results for 30 minutes
- Parallel metadata fetching for better performance

features/wallet/api/src/main/kotlin/io/element/android/features/wallet/api/CardanoClient.kt

@@ -81,4 +81,15 @@ interface CardanoClient {
      * @return Bech32 Cardano address if handle exists, null if not found
      */
     suspend fun resolveHandle(handle: String): Result<String?>
+
+    /**
+     * Get CIP-25 NFT metadata for a specific asset.
+     *
+     * Uses the Koios asset_info endpoint to fetch onchain_metadata.
+     *
+     * @param policyId The minting policy ID (hex, 56 chars)
+     * @param assetName The asset name (hex encoded)
+     * @return [NftMetadata] if CIP-25 metadata exists, null otherwise
+     */
+    suspend fun getNftMetadata(policyId: String, assetName: String): Result<NftMetadata?>
 }

features/wallet/api/src/main/kotlin/io/element/android/features/wallet/api/NftMetadata.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2026 Sulkta Coop.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package io.element.android.features.wallet.api
+
+/**
+ * CIP-25 NFT metadata parsed from Koios asset_info response.
+ *
+ * @property name The NFT name
+ * @property image Resolved HTTP URL for the image (IPFS gateway or direct HTTPS)
+ * @property description NFT description if available
+ * @property rawMetadata Original metadata map for additional fields
+ */
+data class NftMetadata(
+    val name: String,
+    val image: String?,
+    val description: String?,
+    val rawMetadata: Map<String, Any>,
+) {
+    companion object {
+        private const val IPFS_GATEWAY = "https://ipfs.io/ipfs/"
+
+        /**
+         * Resolve IPFS URLs to HTTP gateway URLs.
+         */
+        fun resolveImageUrl(url: String?): String? {
+            if (url == null) return null
+            return when {
+                url.startsWith("ipfs://") -> IPFS_GATEWAY + url.removePrefix("ipfs://")
+                url.startsWith("Qm") -> IPFS_GATEWAY + url // Direct IPFS hash
+                url.startsWith("https://") || url.startsWith("http://") -> url
+                else -> null
+            }
+        }
+
+        /**
+         * Join array-based image URL (some NFTs split the URL across multiple strings).
+         */
+        fun joinImageParts(parts: List<String>?): String? {
+            if (parts.isNullOrEmpty()) return null
+            return resolveImageUrl(parts.joinToString(""))
+        }
+    }
+}