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/tests/test_models.py

@@ -64,6 +64,10 @@ def test_http_routes_publish_response_schemas():
     for path, operations in spec["paths"].items():
         if path.startswith("/api/"):
             for operation in operations.values():
+                if "204" in operation["responses"]:
+                    assert path in {"/api/conversations/current", "/api/conversations/current/interrupt"}
+                    assert "content" not in operation["responses"]["204"]
+                    continue
                 schema = operation["responses"]["200"]["content"]["application/json"]["schema"]
                 assert "$ref" in schema, path
     allocation = spec["components"]["schemas"]["AllocationResponse"]