Phase 2: analytics rollups, geo breakdown, event feed (backend)

- Idempotent hourly rollup (run_rollup, INSERT ... ON CONFLICT DO UPDATE into
  analytics_rollups_hourly) + Tokio background task (startup then hourly)
- GET /v1/cards/{id}/analytics/geo — country-grouped visit counts
- GeoResolver trait: real MaxMind under the `geoip` feature, no-op default;
  raw IP resolved then discarded (only hash + coarse country/city persisted)
- analytics_events now store country/city; rollups read query for the dashboard

2 new tests (geo grouping, rollup aggregation + idempotency); 75 backend tests.
fmt + clippy clean; geoip feature compiles.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

cardclaws-backend/crates/cardclaws-api/src/lib.rs

@@ -8,6 +8,7 @@ pub mod assets;
 pub mod cache;
 pub mod email;
 pub mod error;
+pub mod geo;
 pub mod handlers;
 pub mod middleware;
 pub mod router;