feat: add jetstream firehose backend with SSE streaming #10

adds rust backend for real-time firehose visualization:
- firehose module connects to jetstream and broadcasts all atproto events
- uses rocketman crate with lexicon ingester pattern
- SSE endpoint at /api/firehose/watch streams filtered events by DID
- auto-reconnects on connection drop

remaining work:
- add UI toggle button and toast notifications in templates
- implement particle animation system in static/app.js
- test with live events

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

implements the visual layer for real-time firehose events:
- watch live toggle button in top-right corner
- toast notifications showing event actions (create/update/delete)
- particle animation system using canvas overlay
- colored particles flow from identity to app circles
- particles: green for create, blue for update, red for delete
- app circles pulse when receiving data
- auto-reconnects on connection drop
- clean shutdown when toggled off

complete implementation:
- backend: rust jetstream connector + SSE endpoint (src/firehose.rs, src/routes.rs)
- frontend: particle system + event handling (static/app.js)
- ui: button, toast, css animations (src/templates.rs)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Add clickable "view record" links to firehose toast notifications that open raw record JSON from user's PDS. Also fix particle animation direction to flow from apps to PDS (correctly showing data writes).

Changes:
- Add /api/record endpoint to fetch individual records
- Refactor firehose to use DID-specific connections via manager
- Add toast link element with hover styling
- Fetch record details for richer toast messages
- Reverse particle flow direction (app → PDS)
- Add "Your PDS" label to identity circle

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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