Refactor schedule and user repositories into modular structure

- Moved schedule repository logic into separate modules for SQLite and PostgreSQL implementations.
- Created a mapping module for shared data structures and mapping functions in the schedule repository.
- Added new mapping module for user repository to handle user data transformations.
- Implemented PostgreSQL and SQLite user repository adapters with necessary CRUD operations.
- Added tests for user repository functionality, including saving, finding, and deleting users.

k-tv-backend/infra/src/channel_repository/mod.rs

@@ -0,0 +1,13 @@
+//! SQLite and PostgreSQL adapters for ChannelRepository
+
+mod mapping;
+
+#[cfg(feature = "sqlite")]
+mod sqlite;
+#[cfg(feature = "postgres")]
+mod postgres;
+
+#[cfg(feature = "sqlite")]
+pub use sqlite::SqliteChannelRepository;
+#[cfg(feature = "postgres")]
+pub use postgres::PostgresChannelRepository;