Refactor event payload handling across adapters

- Introduced `event-payload` crate to centralize event payload definitions.
- Updated NATS and PostgreSQL adapters to use the new `EventPayload` type.
- Removed redundant event payload definitions and conversion implementations from NATS and PostgreSQL adapters.
- Simplified SQLite event queue to utilize the new `EventPayload`.
- Refactored wiring functions for PostgreSQL and SQLite to improve database connection handling and migration.
- Cleaned up presentation and worker crates by removing unused event publisher dependencies and related wiring functions.

crates/presentation/Cargo.toml

@@ -49,7 +49,6 @@ metadata = { workspace = true }
 poster-fetcher = { workspace = true }
 poster-storage = { workspace = true }
 template-askama = { workspace = true }
-event-publisher = { workspace = true }
 nats = { workspace = true, optional = true }
 rss = { workspace = true }
 export = { workspace = true }