feat(wallet): ADA Handle resolution ($handle → address)

- Add resolveHandle() to CardanoClient interface
- Implement via Koios asset_addresses API with Handle policy ID
- Add HandleResolved state to RecipientResolutionState
- Detect $handle prefix in PaymentEntryPresenter
- Show "Resolved from $handle ✓" card in PaymentEntryView
- 1-hour in-memory cache for handle lookups
- Case-insensitive handle resolution (normalize to lowercase)
- Add resolveHandle to FakeCardanoClient for testing

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

@@ -70,4 +70,15 @@ interface CardanoClient {
      * @return List of [TxSummary] objects, most recent first
      */
     suspend fun getAddressTransactions(address: String, limit: Int = 20): Result<List<TxSummary>>
+
+    /**
+     * Resolve an ADA Handle to a Cardano address.
+     *
+     * ADA Handles are human-readable names (e.g., $cobb) that resolve to Cardano addresses.
+     * Handle resolution is case-insensitive.
+     *
+     * @param handle Handle name WITHOUT the $ prefix (e.g., "cobb" not "$cobb")
+     * @return Bech32 Cardano address if handle exists, null if not found
+     */
+    suspend fun resolveHandle(handle: String): Result<String?>
 }