feat: critical flag toggle on focus items

Adds a clickable flag marker (⚑) on each focus row to mark items as
critical. Red when active, subtle when inactive. Toggle via POST.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routers/focus.py

@@ -592,6 +592,15 @@ async def toggle_focus(focus_id: str, request: Request, db: AsyncSession = Depen
     return RedirectResponse(url=referer, status_code=303)
 
 
+@router.post("/{focus_id}/toggle-critical")
+async def toggle_critical(focus_id: str, request: Request, db: AsyncSession = Depends(get_db)):
+    repo = BaseRepository("daily_focus", db)
+    item = await repo.get(focus_id)
+    if item:
+        await repo.update(focus_id, {"critical": not item.get("critical", False)})
+    return RedirectResponse(url="/focus", status_code=303)
+
+
 @router.post("/{focus_id}/remove")
 async def remove_from_focus(focus_id: str, request: Request, db: AsyncSession = Depends(get_db)):
     repo = BaseRepository("daily_focus", db)