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/affinity_linux.go

@@ -38,8 +38,15 @@ func SchedSetaffinity(pid int, set *CPUSet) error {
 
 // Zero clears the set s, so that it contains no CPUs.
 func (s *CPUSet) Zero() {
+	clear(s[:])
+}
+
+// Fill adds all possible CPU bits to the set s. On Linux, [SchedSetaffinity]
+// will silently ignore any invalid CPU bits in [CPUSet] so this is an
+// efficient way of resetting the CPU affinity of a process.
+func (s *CPUSet) Fill() {
 	for i := range s {
-		s[i] = 0
+		s[i] = ^cpuMask(0)
 	}
 }