feat(mcp): local MCP server exposes voicebox.* tools to AI agents

Mounts FastMCP at /mcp (Streamable HTTP) so Claude Code, Cursor,
Windsurf, and the VS Code MCP extensions can call voicebox.speak,
voicebox.transcribe, voicebox.list_captures, and voicebox.list_profiles
against the running Voicebox server.

Backend
- new backend/mcp_server package (tools, middleware, profile resolve,
  pub/sub events); named mcp_server to avoid shadowing the installed mcp
  PyPI package FastMCP imports internally
- app.py migrated from @app.on_event to lifespan= so FastMCP's session
  manager cohabits with Voicebox's startup/shutdown
- new MCPClientBinding table + /mcp/bindings CRUD; ClientIdMiddleware
  reads X-Voicebox-Client-Id into a ContextVar and stamps last_seen_at
- profile resolution precedence: explicit -> per-client binding ->
  capture_settings.default_playback_voice_id
- POST /speak REST wrapper for non-MCP callers (shell, ACP, A2A)
- GET /events/speak SSE broadcasts speak-start / speak-end so the pill
  surfaces agent-initiated speech
- backend/mcp_shim proxy (plain httpx) for stdio-only MCP clients
- PyInstaller spec updates + new --shim build target (~18 MB)

Frontend
- Settings -> MCP page with HTTP / stdio / claude-mcp-add copy snippets,
  default voice picker, per-client bindings table, connection status
- useMCPBindings, useSpeakEvents hooks
- CapturePill gains 'speaking' state; DictateWindow subscribes to SSE
  and emits dictate:show so the Rust side surfaces the pill window

Native
- tauri.conf.json externalBin now includes voicebox-mcp
- show_dictate_window helper + dictate:show listener in main.rs
- (also in this commit: InputMonitoringGate UX, hotkey_monitor tweaks,
  landing footer/navbar updates, new overview docs for captures /
  dictation / mcp-server / voice-personalities)

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

backend/services/profiles.py

@@ -275,6 +275,27 @@ async def get_profile(
     return _profile_to_response(profile)
 
 
+def get_profile_orm_by_name_or_id(
+    name_or_id: str,
+    db: Session,
+) -> DBVoiceProfile | None:
+    """Resolve a profile from a user-supplied string that may be either id or name.
+
+    Id is tried first (fast path, matches UUIDs). Name fallback is
+    case-insensitive so agents can say "Morgan" regardless of casing.
+    """
+    if not name_or_id:
+        return None
+    row = db.query(DBVoiceProfile).filter(DBVoiceProfile.id == name_or_id).first()
+    if row is not None:
+        return row
+    return (
+        db.query(DBVoiceProfile)
+        .filter(func.lower(DBVoiceProfile.name) == name_or_id.lower())
+        .first()
+    )
+
+
 async def get_profile_samples(
     profile_id: str,
     db: Session,