android: add multi-account switching foundation in settings

android/CHANGELOG.md

@@ -731,3 +731,19 @@
   - primary profile info card,
   - tab-like section (`Posts/Archived/Gifts`) with placeholder content,
   - inline edit card (name/username/bio/avatar URL) with existing save/upload behavior preserved.
+
+### Step 110 - Multi-account foundation (switch active account)
+- Extended `TokenRepository` to support account list and active-account switching:
+  - observe/list stored accounts,
+  - get active account id,
+  - switch/remove account,
+  - clear all tokens.
+- Reworked `EncryptedPrefsTokenRepository` storage model:
+  - stores tokens per `userId` and account metadata list in encrypted prefs,
+  - migrates legacy single-account keys on first run,
+  - preserves active account pointer.
+- `NetworkAuthRepository` now upserts account metadata after auth/me calls.
+- Added `Settings` UI account section:
+  - shows saved accounts,
+  - allows switch/remove,
+  - triggers auth recheck + chats reload on switch.