implemented git sync for app templates

CLAUDE.md

@@ -33,7 +33,9 @@ deploy-felhom-compose/
 │   ├── internal/
 │   │   ├── config/          # YAML config loading
 │   │   ├── stacks/          # Docker Compose operations, deploy flow
+│   │   ├── sync/            # Git sync — periodic pull of app catalog repo
 │   │   ├── api/             # REST API endpoints
+│   │   ├── system/          # System info (memory, disk)
 │   │   └── web/             # Dashboard UI (embedded HTML/CSS templates)
 │   ├── Dockerfile
 │   ├── Makefile
@@ -98,6 +100,19 @@ ssh kisfenyo@192.168.0.162 "cd /opt/docker/felhom-controller && docker pull gite
 - `app.yaml` persists deploy config; `deployed: true` flag controls UI state
 - Password fields require explicit user input or generation (no silent auto-fill)
 
+## Git sync module (internal/sync)
+
+- Uses `os/exec` to call `git` CLI — no Go git library dependency
+- On startup: clones repo to `{data_dir}/catalog-cache/` (shallow clone, `--depth 1`)
+- Periodically: `git fetch --depth 1` + `git reset --hard origin/{branch}`
+- Copies only `docker-compose.yml` and `.felhom.yml` to stacks dir
+- **Never overwrites** `app.yaml` or `.env` — these contain deployed secrets
+- Content-hash comparison (SHA-256) — only writes if file actually changed
+- After sync, triggers `ScanStacks()` rescan for dashboard update
+- `POST /api/sync` triggers immediate sync (30s debounce)
+- "Sablonok frissítése" button on Alkalmazások page
+- Sync status exposed in `/api/system/info` response
+
 ## Important lessons learned
 
 1. `PAPERLESS_OCR_LANGUAGES` (plural, with S) **installs** tesseract packs; `PAPERLESS_OCR_LANGUAGE` (singular) **selects** which to use