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/cpu/cpuid/cpuid.go

@@ -0,0 +1,32 @@
+// Package cpuid provides generic types used to represent CPU features supported
+// by the architecture.
+package cpuid
+
+// CPU is a bitset of feature flags representing the capabilities of various CPU
+// architeectures that this package provides optimized assembly routines for.
+//
+// The intent is to provide a stable ABI between the Go code that generate the
+// assembly, and the program that uses the library functions.
+type CPU uint64
+
+// Feature represents a single CPU feature.
+type Feature uint64
+
+const (
+	// None is a Feature value that has no CPU features enabled.
+	None Feature = 0
+	// All is a Feature value that has all CPU features enabled.
+	All Feature = 0xFFFFFFFFFFFFFFFF
+)
+
+func (cpu CPU) Has(feature Feature) bool {
+	return (Feature(cpu) & feature) == feature
+}
+
+func (cpu *CPU) Set(feature Feature, enabled bool) {
+	if enabled {
+		*cpu |= CPU(feature)
+	} else {
+		*cpu &= ^CPU(feature)
+	}
+}