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/ifreq_linux.go

@@ -3,12 +3,10 @@
 // license that can be found in the LICENSE file.
 
 //go:build linux
-// +build linux
 
 package unix
 
 import (
-	"bytes"
 	"unsafe"
 )
 
@@ -45,13 +43,7 @@ func NewIfreq(name string) (*Ifreq, error) {
 
 // Name returns the interface name associated with the Ifreq.
 func (ifr *Ifreq) Name() string {
-	// BytePtrToString requires a NULL terminator or the program may crash. If
-	// one is not present, just return the empty string.
-	if !bytes.Contains(ifr.raw.Ifrn[:], []byte{0x00}) {
-		return ""
-	}
-
-	return BytePtrToString(&ifr.raw.Ifrn[0])
+	return ByteSliceToString(ifr.raw.Ifrn[:])
 }
 
 // According to netdevice(7), only AF_INET addresses are returned for numerous
@@ -119,9 +111,7 @@ func (ifr *Ifreq) SetUint32(v uint32) {
 // clear zeroes the ifreq's union field to prevent trailing garbage data from
 // being sent to the kernel if an ifreq is reused.
 func (ifr *Ifreq) clear() {
-	for i := range ifr.raw.Ifru {
-		ifr.raw.Ifru[i] = 0
-	}
+	clear(ifr.raw.Ifru[:])
 }
 
 // TODO(mdlayher): export as IfreqData? For now we can provide helpers such as