feat: theme-grouped pickers, theme-session content panel, theme/topic naming

- Admin Topic Quizzes (was Quizzes): topics are now grouped under
  collapsible theme headers with per-theme counts. Topics without a
  theme fall into a "No theme" bucket rendered last.
- /topic-test picker: eligible topics grouped by theme so learners can
  scan a curriculum theme and drill its topics on demand.
- Fix admin Theme Content panel (was Learning Content): it was empty
  because content moved to the theme_sessions collection in an earlier
  refactor while the panel still queried the legacy per-topic content
  table. Rewrites ContentManager to read db.getAllThemeSessions and
  render the emit_theme_session schema (title, intro, topic sections,
  connections, key takeaways). Adds db.getAllThemeSessions and
  db.deleteThemeSession.
- Disambiguate theme vs topic across the app: the weekly curriculum
  test is now "Theme Test" (nav, page heading, Dashboard card, button,
  explainer); the on-demand bank test stays "Topic Test". Admin nav
  also clarified to "Theme Content" / "Topic Quizzes".

No schema changes. 85/85 tests still pass, build green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/pages/Dashboard.jsx

@@ -111,8 +111,8 @@ const Dashboard = () => {
   };
 
   const explainerSteps = [
-    { icon: BookOpen, title: 'Learn', text: 'Each week you get one topic from the knowledge base. Work through the learning session at your own pace.' },
-    { icon: CheckSquare, title: 'Test', text: 'Once your learning session is done, take the 5-question test to lock in what you learned and earn points.' },
+    { icon: BookOpen, title: 'Learn', text: 'Each week the curriculum gives you a theme — a small set of related topics from the knowledge base. Work through the theme session at your own pace.' },
+    { icon: CheckSquare, title: 'Theme Test', text: 'When your theme session is done, take the 5-question theme test to lock in what you learned and earn points. You can also take an on-demand Topic Test anytime to drill a single topic.' },
     { icon: Trophy, title: 'Climb', text: 'Points add up on the leaderboard. The curriculum runs in perpetual 26-week cycles, so there is always a next step.' },
     { icon: Sparkles, title: 'Ask R42', text: 'R42, your AI study buddy, is on every screen (bottom-right). Ask it anything about your topic or the platform.' },
   ];
@@ -159,7 +159,7 @@ const Dashboard = () => {
               </div>
               <p className="text-fg-muted text-sm">
                 A perpetual learning loop that keeps you current with the company knowledge base.
-                Use the navigation at the top (Home, Learn, Test, Leaderboard) to move around.
+                Use the navigation at the top (Home, Learn, Theme Test, Topic Test, Leaderboard) to move around.
               </p>
             </div>
           </div>
@@ -255,21 +255,21 @@ const Dashboard = () => {
         <Card className="flex flex-col border border-bg-warm" hoverable>
           <div className="flex justify-between items-start mb-4">
             <div>
-              <h3 className="text-xl">Testing</h3>
-              <p className="text-fg-muted text-sm mt-1">Weekly test — 5 questions</p>
+              <h3 className="text-xl">Theme Test</h3>
+              <p className="text-fg-muted text-sm mt-1">This week's theme — 5 questions</p>
             </div>
             {testResult ? <Tag variant="success">Score: {testResult.percentage}%</Tag> : <Tag variant="default">To Do</Tag>}
           </div>
           <div className="flex-1 flex items-center justify-center py-6 text-fg-subtle">
-            {!learnDone ? 'Complete your learning session first' : testResult ? 'Test completed for this week' : 'Ready to test your knowledge'}
+            {!learnDone ? 'Complete your theme session first' : testResult ? 'Theme test completed for this week' : 'Ready to test your knowledge'}
           </div>
           {learnDone && !testResult ? (
             <Link to="/test" className="mt-auto">
-              <Button className="w-full">Start Test</Button>
+              <Button className="w-full">Start Theme Test</Button>
             </Link>
           ) : (
             <Link to="/test" className="mt-auto">
-              <Button variant="outline" className="w-full">{testResult ? 'View Results' : 'Start Test'}</Button>
+              <Button variant="outline" className="w-full">{testResult ? 'View Results' : 'Start Theme Test'}</Button>
             </Link>
           )}
         </Card>