Add podcast playback, Fountain.fm cards, V4V streaming, fix notifications

Podcast feature:
- Podcast discovery via Podcast Index API (trending + search)
- Persistent player bar with play/pause, seek, speed (1x/1.5x/2x), volume
- Audio persists across view navigation, resumes from saved position
- Fountain.fm URL detection in feed with rich playable cards
- "Play in Wrystr" button on inline audio blocks
- V4V streaming sats via NWC (LNURL-pay, 5min accumulation, split payments)
- Share what you're listening to (publish note with confirm)
- Space key toggles play/pause globally

Notification fixes:
- Per-notification read tracking (click to mark read) instead of mark-all-on-open
- Read notifications persist at 50% opacity, unread get accent border
- Always fetches last 7 days, keeps 15 most recent
- Filter out own replies from notifications
- Sidebar badge shows only unread count

src/App.tsx

@@ -18,6 +18,8 @@ import { DMView } from "./components/dm/DMView";
 import { NotificationsView } from "./components/notifications/NotificationsView";
 import { BookmarkView } from "./components/bookmark/BookmarkView";
 import { HashtagFeed } from "./components/feed/HashtagFeed";
+import { PodcastsView } from "./components/podcast/PodcastsView";
+import { PodcastPlayerBar } from "./components/podcast/PodcastPlayerBar";
 import { HelpModal } from "./components/shared/HelpModal";
 import { useUIStore } from "./stores/ui";
 import { useUpdater } from "./hooks/useUpdater";
@@ -102,8 +104,10 @@ function App() {
         {currentView === "notifications" && <NotificationsView />}
         {currentView === "bookmarks" && <BookmarkView />}
         {currentView === "hashtag" && <HashtagFeed />}
+        {currentView === "podcasts" && <PodcastsView />}
       </main>
       </div>
+      <PodcastPlayerBar />
       {showHelp && <HelpModal onClose={toggleHelp} />}
     </div>
   );