feat(mcp): port the server to MCP Python SDK v2 (FastMCP → MCPServer) (#2196)

- server.py: `mcp.server.mcpserver.MCPServer`; StrictArgsFastMCP becomes
  StrictArgsMCPServer, whose call_tool takes and forwards v2's `context`
  and raises ToolError (the SDK logs anything else as an unexpected crash;
  the message reaches the caller either way).
- stateless_http and transport_security moved from the constructor to
  `streamable_http_app(...)` in mount_mcp, with their reasons.
- Per-request user identity is unchanged: the contextvar set around the
  ASGI call reaches the handler on both v2 paths (legacy stateless spawns
  from the request task; the 2026-07-28 modern path opens its task group
  inside the request).
- pyproject: mcp[cli]>=2.2, no ceiling (installs are --locked). uv.lock
  regenerated with --upgrade-package mcp in the ci-python image: only mcp
  and its own dependencies moved (106 → 110 packages).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_mcp_endpoint.py

@@ -3,7 +3,7 @@
 These exercise the ASGI dispatch + auth middleware by driving the app's ASGI
 callable directly. We avoid Quart's test_client() because it expects Quart's
 request pipeline to set `app._preserved_context` as a side effect, but our
-ASGI middleware forwards /mcp requests to FastMCP without touching the Quart
+ASGI middleware forwards /mcp requests to MCPServer without touching the Quart
 pipeline (correct production behavior), which causes test_client to fail on
 teardown.
 
@@ -85,12 +85,12 @@ async def test_mcp_endpoint_invalid_token_returns_401():
 
 @pytest.mark.asyncio
 async def test_mcp_endpoint_valid_token_passes_auth():
-    """With a valid Bearer, the request must successfully reach FastMCP's
+    """With a valid Bearer, the request must successfully reach MCPServer's
     initialize handler. Asserting `!= 401` is too weak: it lets a 404 from
-    a path-mismatch (the original bug) through. FastMCP responds 200 to a
+    a path-mismatch (the original bug) through. MCPServer responds 200 to a
     well-formed initialize handshake.
 
-    FastMCP's session manager normally starts via Quart's @before_serving
+    MCPServer's session manager normally starts via Quart's @before_serving
     hook in production. This raw-ASGI test doesn't go through Quart's
     serving lifecycle, so we manually enter the session manager."""
     fake_key = MagicMock()
@@ -113,7 +113,7 @@ async def test_mcp_endpoint_valid_token_passes_auth():
             status, _ = await _send_request(
                 app, "POST", "/mcp",
                 headers={
-                    # FastMCP's transport_security module enforces a Host
+                    # MCPServer's transport_security module enforces a Host
                     # header (DNS-rebinding protection); without it the
                     # request gets a 421 Misdirected Request.
                     "Host": "testserver",
@@ -123,7 +123,7 @@ async def test_mcp_endpoint_valid_token_passes_auth():
                 },
                 body=initialize_body,
             )
-    assert status == 200, f"expected 200 from FastMCP initialize, got {status}"
+    assert status == 200, f"expected 200 from MCPServer initialize, got {status}"
 
 
 # Note: there's no explicit "non-/mcp paths bypass the middleware" test here