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/github.com/segmentio/asm/ascii/equal_fold_default.go

@@ -0,0 +1,60 @@
+//go:build purego || !amd64
+// +build purego !amd64
+
+package ascii
+
+// EqualFoldString is a version of strings.EqualFold designed to work on ASCII
+// input instead of UTF-8.
+//
+// When the program has guarantees that the input is composed of ASCII
+// characters only, it allows for greater optimizations.
+func EqualFoldString(a, b string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+
+	var cmp byte
+
+	for len(a) >= 8 {
+		cmp |= lowerCase[a[0]] ^ lowerCase[b[0]]
+		cmp |= lowerCase[a[1]] ^ lowerCase[b[1]]
+		cmp |= lowerCase[a[2]] ^ lowerCase[b[2]]
+		cmp |= lowerCase[a[3]] ^ lowerCase[b[3]]
+		cmp |= lowerCase[a[4]] ^ lowerCase[b[4]]
+		cmp |= lowerCase[a[5]] ^ lowerCase[b[5]]
+		cmp |= lowerCase[a[6]] ^ lowerCase[b[6]]
+		cmp |= lowerCase[a[7]] ^ lowerCase[b[7]]
+
+		if cmp != 0 {
+			return false
+		}
+
+		a = a[8:]
+		b = b[8:]
+	}
+
+	switch len(a) {
+	case 7:
+		cmp |= lowerCase[a[6]] ^ lowerCase[b[6]]
+		fallthrough
+	case 6:
+		cmp |= lowerCase[a[5]] ^ lowerCase[b[5]]
+		fallthrough
+	case 5:
+		cmp |= lowerCase[a[4]] ^ lowerCase[b[4]]
+		fallthrough
+	case 4:
+		cmp |= lowerCase[a[3]] ^ lowerCase[b[3]]
+		fallthrough
+	case 3:
+		cmp |= lowerCase[a[2]] ^ lowerCase[b[2]]
+		fallthrough
+	case 2:
+		cmp |= lowerCase[a[1]] ^ lowerCase[b[1]]
+		fallthrough
+	case 1:
+		cmp |= lowerCase[a[0]] ^ lowerCase[b[0]]
+	}
+
+	return cmp == 0
+}