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/shared/hooks/useAudioTransmit.ts

@@ -0,0 +1,49 @@
+// ─── Audio transmit hook — captures mic, encodes to PCM, sends via WebSocket ──
+import { useCallback, useRef, useState } from "react";
+
+const SAMPLE_RATE = 24000;
+
+export function useAudioTransmit(
+  socketRef: { readonly current: WebSocket | null },
+) {
+  const [isStreaming, setIsStreaming] = useState(false);
+  const streamRef = useRef<MediaStream | null>(null);
+  const audioContextRef = useRef<AudioContext | null>(null);
+  const processorRef = useRef<ScriptProcessorNode | null>(null);
+
+  const stop = useCallback(() => {
+    setIsStreaming(false);
+    if (processorRef.current) { processorRef.current.disconnect(); processorRef.current = null; }
+    if (audioContextRef.current) { audioContextRef.current.close(); audioContextRef.current = null; }
+    if (streamRef.current) { for (const track of streamRef.current.getTracks()) track.stop(); streamRef.current = null; }
+  }, []);
+
+  const start = useCallback(async () => {
+    const stream = await navigator.mediaDevices.getUserMedia({ audio: true });
+    streamRef.current = stream;
+    setIsStreaming(true);
+    const AudioContextCtor = window.AudioContext || (window as unknown as { webkitAudioContext: typeof AudioContext }).webkitAudioContext;
+    const audioContext = new AudioContextCtor({ sampleRate: SAMPLE_RATE });
+    audioContextRef.current = audioContext;
+    const source = audioContext.createMediaStreamSource(stream);
+    const processor = audioContext.createScriptProcessor(4096, 1, 1);
+    processorRef.current = processor;
+    source.connect(processor);
+    processor.connect(audioContext.destination);
+    processor.onaudioprocess = (event) => {
+      if (!socketRef.current || socketRef.current.readyState !== WebSocket.OPEN) return;
+      const inputData = event.inputBuffer.getChannelData(0);
+      const pcmData = new Int16Array(inputData.length);
+      for (let i = 0; i < inputData.length; i++) pcmData[i] = Math.max(-1, Math.min(1, inputData[i])) * 32767;
+      // BUG 2 FIX: slice() to create independent copy of the ArrayBuffer
+      socketRef.current.send(pcmData.buffer.slice(0));
+    };
+  }, [socketRef]);
+
+  const toggle = useCallback(async () => {
+    if (isStreaming) stop();
+    else await start();
+  }, [isStreaming, start, stop]);
+
+  return { isStreaming, toggle, stop, start };
+}