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/test/src/main/kotlin/io/element/android/features/wallet/test/FakeCardanoClient.kt

@@ -9,6 +9,7 @@ package io.element.android.features.wallet.test
 import io.element.android.features.wallet.api.CardanoClient
 import io.element.android.features.wallet.api.CardanoException
 import io.element.android.features.wallet.api.NativeAsset
+import io.element.android.features.wallet.api.NftMetadata
 import io.element.android.features.wallet.api.ProtocolParameters
 import io.element.android.features.wallet.api.TxStatus
 import io.element.android.features.wallet.api.TxSummary
@@ -24,6 +25,7 @@ import io.element.android.features.wallet.api.UtxoAsset
  * - Rate limiting
  * - Transaction lifecycle (pending → confirmed)
  * - ADA Handle resolution
+ * - NFT metadata
  */
 class FakeCardanoClient : CardanoClient {
     // Configurable responses
@@ -34,6 +36,7 @@ class FakeCardanoClient : CardanoClient {
     var assets = mutableMapOf<String, List<NativeAsset>>()
     var transactions = mutableMapOf<String, List<TxSummary>>()
     var handles = mutableMapOf<String, String>() // handle name (without $) -> address
+    var nftMetadata = mutableMapOf<String, NftMetadata>() // policyId+assetName -> metadata
 
     // Error simulation
     var shouldFailWithNetworkError = false
@@ -67,6 +70,8 @@ class FakeCardanoClient : CardanoClient {
         private set
     var resolveHandleCallCount = 0
         private set
+    var getNftMetadataCallCount = 0
+        private set
 
     /**
      * Represents a submitted transaction for testing.
@@ -204,6 +209,20 @@ class FakeCardanoClient : CardanoClient {
         return Result.success(address)
     }
 
+    override suspend fun getNftMetadata(policyId: String, assetName: String): Result<NftMetadata?> {
+        getNftMetadataCallCount++
+
+        if (shouldFailWithNetworkError) {
+            return Result.failure(CardanoException.NetworkException("Simulated network error"))
+        }
+        if (shouldFailWithRateLimit) {
+            return Result.failure(CardanoException.RateLimitException(retryAfterMs = 1000L))
+        }
+
+        val key = "$policyId$assetName"
+        return Result.success(nftMetadata[key])
+    }
+
     // Helper methods for test setup
 
     /**
@@ -270,6 +289,13 @@ class FakeCardanoClient : CardanoClient {
         handles[handle.lowercase().trim()] = address
     }
 
+    /**
+     * Configures NFT metadata for an asset.
+     */
+    fun givenNftMetadata(policyId: String, assetName: String, metadata: NftMetadata) {
+        nftMetadata["$policyId$assetName"] = metadata
+    }
+
     /**
      * Resets all state and counters.
      */
@@ -281,6 +307,7 @@ class FakeCardanoClient : CardanoClient {
         assets.clear()
         transactions.clear()
         handles.clear()
+        nftMetadata.clear()
         shouldFailWithNetworkError = false
         shouldFailWithRateLimit = false
         submitShouldFail = false
@@ -294,6 +321,7 @@ class FakeCardanoClient : CardanoClient {
         getAddressAssetsCallCount = 0
         getAddressTransactionsCallCount = 0
         resolveHandleCallCount = 0
+        getNftMetadataCallCount = 0
         protocolParameters = ProtocolParameters(
             minFeeA = 44L,
             minFeeB = 155381L,