feat: app-to-app integration framework + OnlyOffice handlers

Generic integration system for connecting deployed apps via toggle UI.
First handlers: OnlyOffice→FileBrowser (config.yaml patch) and
OnlyOffice→Nextcloud (occ CLI). Lifecycle hooks auto-suspend on
stop and re-apply on start.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,18 @@
 ## Changelog
 
+### v0.31.0 — App-to-App Integration Framework (2026-02-25)
+
+#### Added
+- **Generic integration framework** (`internal/integrations/`) — Extensible system for connecting deployed apps to each other via toggle switches on the provider's app info page
+- **OnlyOffice → FileBrowser integration** — Toggle enables document editing in FileBrowser by patching `config.yaml` with OnlyOffice URL and JWT secret
+- **OnlyOffice → Nextcloud integration** — Toggle installs and configures the OnlyOffice connector app via `occ` CLI commands
+- **Integration lifecycle hooks** — Integrations auto-suspend when provider or target stops, auto-re-enable when both are running again, permanently removed on app deletion
+- **Integration API endpoints** — `GET /api/integrations/{provider}` (list), `POST /api/integrations/{provider}/{target}` (toggle)
+- **Integration UI** — "Integrációk" section on app info page with toggle switches, status badges, and target availability indicators
+- **`IntegrationDef`** in `.felhom.yml` metadata — Apps can declare integrations with target app slug, label, and description
+- **`IntegrationState`** in `settings.json` — Persistent integration state with enabled/status/error tracking
+- **SyncFileBrowserMounts re-apply** — After config regeneration (which overwrites config.yaml), active integrations are automatically re-applied
+
 ### v0.30.7 — Monitoring: Fix Memory Legend Overflow (2026-02-25)
 
 #### Fixed