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/cpu/parse.go

@@ -0,0 +1,43 @@
+// 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.
+
+package cpu
+
+import "strconv"
+
+// parseRelease parses a dot-separated version number. It follows the semver
+// syntax, but allows the minor and patch versions to be elided.
+//
+// This is a copy of the Go runtime's parseRelease from
+// https://golang.org/cl/209597.
+func parseRelease(rel string) (major, minor, patch int, ok bool) {
+	// Strip anything after a dash or plus.
+	for i := range len(rel) {
+		if rel[i] == '-' || rel[i] == '+' {
+			rel = rel[:i]
+			break
+		}
+	}
+
+	next := func() (int, bool) {
+		for i := range len(rel) {
+			if rel[i] == '.' {
+				ver, err := strconv.Atoi(rel[:i])
+				rel = rel[i+1:]
+				return ver, err == nil
+			}
+		}
+		ver, err := strconv.Atoi(rel)
+		rel = ""
+		return ver, err == nil
+	}
+	if major, ok = next(); !ok || rel == "" {
+		return
+	}
+	if minor, ok = next(); !ok || rel == "" {
+		return
+	}
+	patch, ok = next()
+	return
+}