fix(sync): Remove .since() filter from database queries in load_existing_events()

Root cause: `last_connected` was set to Timestamp::now() BEFORE
load_existing_events() was called (line 425), causing the database
query to filter out all existing events with .since(current_time).

The query became: SELECT * FROM events WHERE created_at >= <now>
Result: 0 events returned (nothing has created_at in the future)

Solution: Remove .since() filter from database queries entirely.
The `last_connected` field is now only used for WebSocket subscription
filters to avoid re-fetching events from remote relays on reconnect.

Rationale for this approach over reordering operations:
- Database queries are fast (indexed by kind and created_at)
- Loading all events on startup ensures consistency
- Eliminates subtle ordering dependency that could break in refactoring
- Cleaner mental model: database = full load, WebSocket = incremental

This fixes the issue where ~190 state events weren't being fetched
after deploying the database query fix (commit 4162c90).

Evidence: Production logs showed "Loaded announcements from database
count=0" when there should have been hundreds of announcements.

0 files changed, 0 insertions, 0 deletions