refactor: implement trait-based DI for TdClient and fix stack overflow

Implement complete trait-based dependency injection pattern for TdClient
to enable testing with FakeTdClient mock. Fix critical stack overflow bugs
caused by infinite recursion in trait implementations.

Breaking Changes:
- App is now generic: App<T: TdClientTrait = TdClient>
- All UI and input handlers are generic over TdClientTrait
- TdClient methods now accessed through trait interface

New Files:
- src/tdlib/trait.rs: TdClientTrait definition with 40+ methods
- src/tdlib/client_impl.rs: TdClientTrait impl for TdClient
- tests/helpers/fake_tdclient_impl.rs: TdClientTrait impl for FakeTdClient

Critical Fixes:
- Fix stack overflow in send_message, edit_message, delete_messages
- Fix stack overflow in forward_messages, current_chat_messages
- Fix stack overflow in current_pinned_message
- All methods now call message_manager directly to avoid recursion

Testing:
- FakeTdClient supports configurable auth_state for auth screen tests
- Added pinned message support in FakeTdClient
- All 196+ tests passing (188 tests + 8 benchmarks)

Dependencies:
- Added async-trait = "0.1"

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/helpers/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod app_builder;
 pub mod fake_tdclient;
+mod fake_tdclient_impl; // TdClientTrait implementation for FakeTdClient
 pub mod snapshot_utils;
 pub mod test_data;