feat: phase 3 + phase 4 complete — v0.4.0

Phase 3:
- Config reload via SIGHUP (handle_signals loop: .hup reloads config, .int/.term shutdown)
- Hot reload: cfg, webhook_routes, ntfy client, dedup updated without restart

Phase 4:
- Silence rules: POST /api/silence?duration=30m, GET /api/silence, DELETE /api/silence
- Grouping: buffer 10s, events grouped with (×N in 10s) suffix
- CI/CD: .gitea/workflows/ci.yml (build + test on push/PR)

Docs:
- ROADMAP.md: phases 3 & 4 marked DONE, version table updated
- ARCHITECTURE.md: synced with actual code

Version: 0.1.0 → 0.4.0 (main.v, v.mod)

v.mod

@@ -1,7 +1,7 @@
 Module {
     name: 'ntfy-bridge'
     description: 'Homelab notification hub — aggregates Gitea, Docker, Uptime Kuma → Ntfy'
-    version: '0.1.0'
+    version: '0.4.0'
     license: 'MIT'
     dependencies: []
     subdirs: ['sources']