fix(activity): show Convert transactions in the feed (#1281)

* fix(activity): show Convert transactions in the feed

A swap spans two mints, so the backend leaves `payment_amount` unset and carries
both amounts in `additional_metadata` instead. `ActivityFeedMessageMapper` only
ever read `payment_amount`, so every Convert cached with a null amount, rate, and
mint — which meant it matched no token's activity query and rendered blank in the
global feed.

- Map multi-mint amounts from `additional_metadata` when `payment_amount` is absent.
- Attribute a Convert to *both* mints, so it appears on the source and destination
  token screens (`MintInvolvement` + the metadata clause in `observeRecentForMint`).
- Render it the way iOS does: overlapping dual-token avatar, from-amount on top,
  `-<fee> Fee` beneath.
- Title the row with the two token names ("Moony -> Jeffy") rather than the
  server's bare "Converted", falling back to the server text until both tokens
  resolve.

Rows cached before this can't be repaired in place (the amounts were never
persisted) and can't be re-fetched either, since sync only walks forward from the
newest cached id. DB 28 -> 29 clears `messages` so the next sync re-seeds from
scratch — the same approach as the existing 1->2, 6->7, 7->8 and 9->10 migrations.

Also fixes a silent data-loss path found alongside it: `MessageDataSource.upsert`
no-oped when the per-user DB wasn't open yet, discarding a whole fetched page
while the coordinator still reported `Synced`. Because every sync path pages
forward from the newest cached id, those notifications were never requested
again. It now fails loudly (matching `observe()`, which already errors on a
missing DB), the mediator turns that into a retryable error, and the coordinator
only reports `Synced` once the write has actually landed.

* test(persistence): cover the v29 feed-clearing migration

Folds in the standalone migration work from #1284, which duplicated the
28 -> 29 clear this branch already carries.

Adds TransactionHistoryMigrationTest, following the hand-rolled pattern
in UserProfileMigrationTest: asserts the feed is emptied, that a
neighbouring table survives, and that it's a no-op on an already-empty
feed.

Also switches Migration28To29 to the onPostMigrate(SQLiteConnection)
overload. Room's SupportSQLiteDatabase variant only fires when the
database is built without a driver, so a future setDriver would turn the
delete into a silent no-op.

Author: bmc08gt

apps/flipcash/core/src/main/kotlin/com/flipcash/app/core/feed/ActivityFeedMessage.kt

@@ -9,9 +9,16 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
 import kotlin.time.Instant
 
+/**
+ * A feed entry paired with the token metadata its row needs.
+ *
+ * [token] is the entry's own token (for a convert, the source side). [toToken] is only set for a
+ * convert, which spans two mints and draws both logos; everything else leaves it null.
+ */
 data class ActivityFeedMessageWithToken(
     val message: ActivityFeedMessage,
-    val token: Token?
+    val token: Token?,
+    val toToken: Token? = null,
 )
 
 data class ActivityFeedMessage(

apps/flipcash/features/balance/src/test/kotlin/com/flipcash/app/balance/internal/WalletLoadingStateTest.kt

@@ -28,6 +28,7 @@ class WalletLoadingStateTest {
         avatar = TransactionAvatar.Generic,
         signedAmountPrefix = "+",
         amount = null,
+        fee = null,
         canCancel = false,
     )