Simplify templates to pure Jinja2 + CodeMirror editor + variable reference

Major template system overhaul:
- TemplateConfig simplified from 21 fields to 9: removed all sub-templates
  (asset_image, asset_video, assets_format, people_format, etc.)
  Users write full Jinja2 with {% for %}, {% if %} inline.
- Default EN/RU templates seeded on first startup (user_id=0, system-owned)
  with proper Jinja2 loops over added_assets, people, albums.
- build_full_context() simplified: passes raw data directly to Jinja2
  instead of pre-rendering sub-templates.
- CodeMirror editor for template slots (HTML syntax highlighting,
  line wrapping, dark theme support via oneDark).
- Variable reference API: GET /api/template-configs/variables returns
  per-slot variable descriptions + asset_fields for loop contexts.
- Variable reference modal in UI: click "{{ }} Variables" next to any
  slot to see available variables with Jinja2 syntax examples.
- Route ordering fix: /variables registered before /{config_id}.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/server/src/immich_watcher_server/main.py

@@ -33,6 +33,33 @@ logging.basicConfig(
 _LOGGER = logging.getLogger(__name__)
 
 
+async def _seed_default_templates():
+    """Create default EN/RU template configs if none exist."""
+    from sqlmodel import func, select
+    from sqlmodel.ext.asyncio.session import AsyncSession
+    from .database.engine import get_engine
+    from .database.models import (
+        TemplateConfig,
+        DEFAULT_TEMPLATE_EN,
+        DEFAULT_TEMPLATE_RU,
+    )
+
+    engine = get_engine()
+    async with AsyncSession(engine) as session:
+        result = await session.exec(select(func.count()).select_from(TemplateConfig))
+        count = result.one()
+        if count > 0:
+            return
+
+        # user_id=0 means system-owned (available to all users)
+        en = TemplateConfig(user_id=0, name="Default EN", icon="mdiTranslate", **DEFAULT_TEMPLATE_EN)
+        ru = TemplateConfig(user_id=0, name="По умолчанию RU", icon="mdiTranslate", **DEFAULT_TEMPLATE_RU)
+        session.add(en)
+        session.add(ru)
+        await session.commit()
+        _LOGGER.info("Seeded default EN and RU template configs")
+
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     """Application lifespan: startup and shutdown."""
@@ -41,6 +68,9 @@ async def lifespan(app: FastAPI):
     await init_db()
     _LOGGER.info("Database initialized at %s", settings.effective_database_url)
 
+    # Seed default templates if none exist
+    await _seed_default_templates()
+
     await start_scheduler()
 
     yield