feat(mcp): connect authenticated AquaPortal tools to Vocero (#1)

Vocero needs to query AquaPortal on behalf of the caller selected by the existing phone link. This adds server-owned conversations and MCP tool execution for voice and HTTP reasoning while leaving the speech pipeline unchanged.

Release notes:

- Added browser-bound conversations that keep backend credentials server-side and isolate callers.
- Connected the eight-tool AquaPortal catalog through authenticated Streamable HTTP with full input schemas and structured results.
- Added bounded multi-step tool execution with cancellation, expiry, and stale-result protection.
- Updated browser bootstrap, tool progress, reasoning headers, and conversation cleanup.
- Disabled legacy unscoped content preloads in MCP mode and documented configuration and deployment constraints.
- Preserved disabled-mode contracts and added local SDK, WebSocket, and browser regression coverage.

Reviewed-on: AquaPortal/s2s#1

vocero-api/vocero_api/core/urls.py

@@ -42,6 +42,8 @@ def _proxy_upstream_url(ws: WebSocket) -> str:
     target = urlsplit(settings.S2S_PROXY_TARGET)
     merged_query = dict(parse_qsl(target.query, keep_blank_values=True))
     merged_query.update(parse_qsl(ws.url.query, keep_blank_values=True))
+    if settings.S2S_MCP_URL:
+        merged_query.pop("conversation_id", None)
     return urlunsplit(
         (
             target.scheme,