Move default templates to .jinja2 files + add live preview + update CLAUDE.md

Templates:
- Default EN/RU templates moved from inline Python strings to
  14 .jinja2 files in templates/{en,ru}/ directory
- Properly formatted with readable indentation and Jinja2
  whitespace control ({%- -%})
- load_default_templates(locale) loads from files on first access
- Seed function uses file loader instead of inline dicts

Preview:
- New POST /api/template-configs/preview-raw endpoint: renders
  arbitrary Jinja2 text with sample data (for live editing preview)
- Route ordering fixed: /variables before /{config_id}

CLAUDE.md:
- Added Frontend Architecture Notes (i18n, Svelte 5 runes, auth
  flow, Tailwind v4 quirks)
- Added Backend Architecture Notes (SQLAlchemy+aiohttp greenlet
  issue, SandboxedEnvironment import, system-owned entities,
  FastAPI route ordering, __pycache__)

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

packages/server/src/immich_watcher_server/main.py

@@ -38,11 +38,7 @@ async def _seed_default_templates():
     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,
-    )
+    from .database.models import TemplateConfig, get_default_templates
 
     engine = get_engine()
     async with AsyncSession(engine) as session:
@@ -52,8 +48,8 @@ async def _seed_default_templates():
             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)
+        en = TemplateConfig(user_id=0, name="Default EN", icon="mdiTranslate", **get_default_templates("en"))
+        ru = TemplateConfig(user_id=0, name="По умолчанию RU", icon="mdiTranslate", **get_default_templates("ru"))
         session.add(en)
         session.add(ru)
         await session.commit()