Add SSO login support

- Add [sso] config section with redirect_uri
- Create mcdsl/sso client when SSO is configured
- Add /login (landing page), /sso/redirect, /sso/callback routes
- Add /logout route
- Update login template with SSO landing page variant
- Bump mcdsl to v1.6.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/git.wntrmute.dev/kyle/goutils/lib/ftime_unix.go

@@ -0,0 +1,38 @@
+//go:build unix || linux || openbsd || (darwin && amd64)
+
+package lib
+
+import (
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+// FileTime contains the changed, modified, and accessed timestamps
+// for a file.
+type FileTime struct {
+	Changed  time.Time
+	Modified time.Time
+	Accessed time.Time
+}
+
+func timeSpecToTime(ts unix.Timespec) time.Time {
+	// The casts to int64 are needed because on 386, these are int32s.
+	return time.Unix(ts.Sec, ts.Nsec)
+}
+
+// LoadFileTime returns a FileTime associated with the file.
+func LoadFileTime(path string) (FileTime, error) {
+	var ft = FileTime{}
+	var st = unix.Stat_t{}
+
+	err := unix.Stat(path, &st)
+	if err != nil {
+		return ft, err
+	}
+
+	ft.Changed = timeSpecToTime(st.Ctim)
+	ft.Modified = timeSpecToTime(st.Mtim)
+	ft.Accessed = timeSpecToTime(st.Atim)
+	return ft, nil
+}