feat(18-02): REST API handlers for /api/v1/* endpoints

- Stats, keys, providers, scan, recon, dorks, config endpoints
- JSON response wrappers with proper tags for all entities
- Filtering, pagination, 404/204/202 status codes
- SSE hub stub (full impl in task 2)
- Resolved merge conflict in schema.sql
- 16 passing tests covering all endpoints

go.mod

@@ -44,6 +44,7 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/emirpasic/gods v1.18.1 // indirect
 	github.com/fsnotify/fsnotify v1.9.0 // indirect
+	github.com/go-chi/chi/v5 v5.2.5 // indirect
 	github.com/go-git/gcfg v1.5.1-0.20230307220236-3a3c6141e376 // indirect
 	github.com/go-git/go-billy/v5 v5.8.0 // indirect
 	github.com/go-viper/mapstructure/v2 v2.4.0 // indirect