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/keyset/keyset.go

@@ -0,0 +1,40 @@
+package keyset
+
+import (
+	"bytes"
+
+	"github.com/segmentio/asm/cpu"
+	"github.com/segmentio/asm/cpu/arm64"
+	"github.com/segmentio/asm/cpu/x86"
+)
+
+// New prepares a set of keys for use with Lookup.
+//
+// An optimized routine is used if the processor supports AVX instructions and
+// the maximum length of any of the keys is less than or equal to 16. If New
+// returns nil, this indicates that an optimized routine is not available, and
+// the caller should use a fallback.
+func New(keys [][]byte) []byte {
+	maxWidth, hasNullByte := checkKeys(keys)
+	if hasNullByte || maxWidth > 16 || !(cpu.X86.Has(x86.AVX) || cpu.ARM64.Has(arm64.ASIMD)) {
+		return nil
+	}
+
+	set := make([]byte, len(keys)*16)
+	for i, k := range keys {
+		copy(set[i*16:], k)
+	}
+	return set
+}
+
+func checkKeys(keys [][]byte) (maxWidth int, hasNullByte bool) {
+	for _, k := range keys {
+		if len(k) > maxWidth {
+			maxWidth = len(k)
+		}
+		if bytes.IndexByte(k, 0) >= 0 {
+			hasNullByte = true
+		}
+	}
+	return
+}