feat: add MCP endpoint exposing calendar tools over Streamable HTTP

Adds a POST /mcp endpoint (github.com/modelcontextprotocol/go-sdk) with
three tools mirroring the existing /calendar logic: get_calendar_today,
get_calendar_for_date and get_holidays. Bumps go.mod to Go 1.25 (required
by the SDK) and vendors the new dependencies. Also fixes an unanchored
.gitignore rule ("domogeek") that was silently excluding all untracked
files under cmd/domogeek/.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hu8wwahgecuCGfesTKCfEd

vendor/golang.org/x/sys/unix/syscall_hurd.go

@@ -0,0 +1,30 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build hurd
+
+package unix
+
+/*
+#include <stdint.h>
+int ioctl(int, unsigned long int, uintptr_t);
+*/
+import "C"
+import "unsafe"
+
+func ioctl(fd int, req uint, arg uintptr) (err error) {
+	r0, er := C.ioctl(C.int(fd), C.ulong(req), C.uintptr_t(arg))
+	if r0 == -1 && er != nil {
+		err = er
+	}
+	return
+}
+
+func ioctlPtr(fd int, req uint, arg unsafe.Pointer) (err error) {
+	r0, er := C.ioctl(C.int(fd), C.ulong(req), C.uintptr_t(uintptr(arg)))
+	if r0 == -1 && er != nil {
+		err = er
+	}
+	return
+}