ui: migrate to shadcn/ui primitives across dialogs, filters, and forms

Adopts shadcn/ui components (Dialog, Button, Input, Select, Popover,
Command, Checkbox, Switch, Toggle, Calendar, etc.) across the app,
replacing hand-rolled modals, dropdowns, and form controls. Adds a
reusable cmdk-backed MultiSelect for the Type, Tags, and Flag filters
so all multi-value filter popovers share one component and layout.

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

frontend/src/App.tsx

@@ -24,6 +24,7 @@ import { usePhotosQuery } from './hooks/usePhotosQuery'
 import { AuthProvider, useAuth } from './contexts/AuthContext'
 import { LoginPage } from './components/auth/LoginPage'
 import { SetupPage } from './components/auth/SetupPage'
+import { TooltipProvider } from '@/components/ui/tooltip'
 
 function MainApp() {
   const [leftSidebarOpen, setLeftSidebarOpen] = useState(true)
@@ -71,6 +72,7 @@ function MainApp() {
   const showRightSidebar = rightSidebarOpen && !isSettings
 
   return (
+    <TooltipProvider delayDuration={300}>
     <div className="flex flex-col h-screen bg-bg text-text">
       <TopBar />
 
@@ -140,6 +142,7 @@ function MainApp() {
       {viewMode === 'preview' && <PreviewView />}
 
     </div>
+    </TooltipProvider>
   )
 }