feat: Discord/Slack/ntfy/Matrix targets, command templates, delete protection, email/matrix bots

- Discord, Slack, ntfy, Matrix notification target types with clients and dispatch
- MatrixBot model + API + frontend in Bots tab
- Command template system fully wired into all handler commands
- Default command templates seeded (EN/RU, 14 slots each)
- Command template editor with variables reference including child fields
- Delete protection on all 10 entity types (409 with consumer details)
- Provider type selector on template config forms
- Target type selector as dropdown with all 7 types
- Response template selector on command config form
- CLAUDE.md: mandatory server restart rule, child properties rule

CLAUDE.md

@@ -2,7 +2,7 @@
 
 ## Development Servers
 
-**IMPORTANT**: When the user requests it OR when backend code changes are made (files in `packages/server/`), you MUST restart the standalone server using this one-liner:
+**MANDATORY**: You MUST restart the backend server IMMEDIATELY after ANY backend code change (files in `packages/server/` or `packages/core/`). Do NOT wait for the user to ask — restart automatically every time. Failure to restart means the user will test against stale code and encounter bugs that don't exist. Use this one-liner:
 ```bash
 PID=$(netstat -ano 2>/dev/null | grep ':8420.*LISTENING' | awk '{print $5}' | head -1) && [ -n "$PID" ] && taskkill //F //PID $PID 2>/dev/null; sleep 1 && cd packages/server && pip install -e . 2>&1 | tail -1 && cd ../.. && NOTIFY_BRIDGE_DATA_DIR=./test-data NOTIFY_BRIDGE_SECRET_KEY=test-secret-key-minimum-32chars nohup python -m uvicorn notify_bridge_server.main:app --host 0.0.0.0 --port 8420 > /dev/null 2>&1 & sleep 3 && curl -s http://localhost:8420/api/health
 ```
@@ -71,3 +71,6 @@ TelegramBot → token, update_mode, bot_username (used as notification target ba
 3. **`packages/server/.../api/template_configs.py`** — `get_template_variables()` endpoint (`event_vars`, `asset_fields`, `album_fields`, `scheduled_vars`, per-slot variable dicts)
 4. **`packages/core/.../templates/defaults/{en,ru}/*.jinja2`** — default template files using the new variables
 5. **`packages/core/.../providers/immich/provider.py`** — `IMMICH_VARIABLES` list (provider-specific variable definitions)
+6. **`packages/server/.../api/command_template_configs.py`** — `get_command_variables()` endpoint (for command response templates)
+
+**IMPORTANT**: Variable reference endpoints MUST document child/nested properties, not only top-level variables. When a variable is a list of dicts (e.g. `assets`, `albums`, `events`, `commands`), the endpoint MUST include a corresponding `*_fields` dict describing the child properties (e.g. `asset_fields: {"id": "...", "filename": "..."}`) so the frontend can show them (e.g. `{{ asset.id }}`, `{{ album.name }}`). Never list only `"assets": "List of asset dicts"` — always specify what fields each dict contains.