chore(vocero): remove the legacy ApiPilot integration (#3)

Vocero now retrieves AquaPortal content through authenticated MCP. This removes the obsolete ApiPilot integration from the API and browser while preserving the separately deployed speech pipeline.

Release notes:

- Removed ApiPilot endpoints, configuration, credential overrides, and HTTP/realtime tool execution.
- Removed browser ApiPilot catalog loading and prompt generation while retaining authenticated MCP discovery.
- Updated regression coverage and operating documentation for the retired routes and settings.

Reviewed-on: AquaPortal/s2s#3

vocero-frontend/README.md

@@ -144,10 +144,11 @@ Markdown replies, JSON/TXT exports, optional browser wake word, TALK/TALKFIRST
 startup modes, and optional backend features are retained. Camera controls and
 quick actions remain absent, matching their disabled state in the old UI.
 
-Native speech stays at the current project's 16 kHz PCM rate. The backend
-continues to own VAD, transcription, model inference, synthesis, upstream
-credentials, and ApiPilot execution. Browser `SpeechSynthesis` is used only
-when the configured external reasoning service returns an answer.
+Native speech stays at the current project's 16 kHz PCM rate. The speech service
+owns VAD, transcription, model inference, and synthesis. The Vocero API owns
+AquaPortal credentials and authenticated MCP discovery/execution. Browser
+`SpeechSynthesis` is used only when the configured external reasoning service
+returns an answer.
 
 Session startup waits for audio initialization and `session.created`, then sends
 `session.update` before microphone audio or the initial greeting. The speech