Add Layouts module with Konva.js builder; smart offline polling; UI improvements

- Move board cards from dashboard to top of boards list page
- Fix Werkzeug duplicate polling (WERKZEUG_RUN_MAIN guard)
- Smart offline polling: fast loop for online boards, slow recheck for offline
- Add manual ping endpoint POST /api/boards/<id>/ping
- Add spin animation CSS for ping button

Layouts module (new):
- app/models/layout.py: Layout model (canvas_json, thumbnail_b64)
- app/routes/layouts.py: 5 routes (list, create, builder, save, delete)
- app/templates/layouts/: list and builder templates
- app/static/js/layout_builder.js: full Konva.js builder engine
- app/static/vendor/konva/: vendored Konva.js 9
- Structure mode: wall, room, door, window, fence, text shapes
- Devices mode: drag relay/input/Sonoff channels onto canvas
- Live view mode: click relays/Sonoff to toggle, socket.io state updates
- Device selection: click to select, remove individual device, Delete key
- Fix door/Arc size persistence across save/reload (outerRadius, scaleX/Y)
- Fix Sonoff devices missing from palette (add makeSonoffChip function)

app/__init__.py

@@ -36,6 +36,7 @@ def create_app(config_name: str = "default") -> Flask:
     from app.routes.api import api_bp
     from app.routes.admin import admin_bp
     from app.routes.sonoff import sonoff_bp
+    from app.routes.layouts import layouts_bp
 
     app.register_blueprint(auth_bp)
     app.register_blueprint(dashboard_bp)
@@ -44,6 +45,7 @@ def create_app(config_name: str = "default") -> Flask:
     app.register_blueprint(api_bp, url_prefix="/api")
     app.register_blueprint(admin_bp, url_prefix="/admin")
     app.register_blueprint(sonoff_bp)
+    app.register_blueprint(layouts_bp, url_prefix="/layouts")
 
     # ── user loader ───────────────────────────────────────────────────────────
     from app.models.user import User
@@ -62,6 +64,7 @@ def create_app(config_name: str = "default") -> Flask:
         # Import all models so their tables are registered before create_all
         from app.models import board, user, workflow  # noqa: F401
         from app.models import sonoff_device  # noqa: F401
+        from app.models import layout  # noqa: F401
         db.create_all()
         _seed_admin(app)
         _add_entities_column(app)