refactor(frontend): major rebuild — feature-sliced architecture + bug fixes + glass-morphism UI

Architecture:
- Feature-sliced directory: entities/, shared/, features/, widgets/
- Consolidated API client (shared/api/client.ts) — all endpoints in one file
- Single WebSocket manager (shared/ws/socket.ts) with typed event bus
- Extracted hooks: useAudioPlayback, useAudioTransmit, useLocalStorage, useUIState
- UI primitives moved to shared/ui/ with barrel export
- Added Skeleton, Toast, MobileTabBar components

Bug fixes (8/8):
1. useMemo→useEffect in RecordingsSubPanel (async side-effect anti-pattern)
2. ArrayBuffer.slice() before WebSocket send (shared buffer bug)
3. Proper useEffect dependency arrays throughout
4. Stable React keys (no index fallbacks)
5. onReanalyze properly awaited (Promise<void> return)
6. monitorGuild memoized with useMemo
7. localStorage validation with shape checking
8. Deleted duplicate socket logic (ws/client.ts removed)

UI polish:
- Glass-morphism design tokens (backdrop-blur, translucent cards)
- Gradient mesh background with subtle radial overlays
- Expandable sidebar + mobile bottom tab bar
- Skeleton loading placeholders
- Audio visualizer with CSS pulse animation

Deleted: src/api/, src/components/, src/hooks/, src/types/, src/ws/, src/lib/
Added: 40 new files across feature-sliced structure

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/live/components/ScreenSubPanel.tsx

@@ -0,0 +1,37 @@
+import { useState } from "react";
+import { Button, Input } from "../../../shared/ui";
+import { MonitorUp, SkipForward, Square } from "lucide-react";
+
+interface ScreenSubPanelProps {
+  onStart: (source: string) => void;
+  onSkip: () => void;
+  onStop: () => void;
+  loading: boolean;
+}
+
+export function ScreenSubPanel({ onStart, onSkip, onStop, loading }: ScreenSubPanelProps) {
+  const [source, setSource] = useState("");
+  const submit = () => { const t = source.trim(); if (!t) return; onStart(t); setSource(""); };
+
+  return (
+    <div className="space-y-4">
+      <Input
+        value={source}
+        onChange={(e) => setSource(e.target.value)}
+        onKeyDown={(e) => e.key === "Enter" && submit()}
+        placeholder="Screen share URL or local file path"
+      />
+      <div className="flex flex-wrap gap-2">
+        <Button disabled={loading || !source.trim()} onClick={submit}>
+          <MonitorUp className="mr-1.5 h-4 w-4" /> Start
+        </Button>
+        <Button variant="secondary" disabled={loading} onClick={onSkip}>
+          <SkipForward className="mr-1.5 h-4 w-4" /> Skip
+        </Button>
+        <Button variant="destructive" disabled={loading} onClick={onStop}>
+          <Square className="mr-1.5 h-4 w-4" /> Stop
+        </Button>
+      </div>
+    </div>
+  );
+}