Initial lookbook implementation

Pinterest-style visual bookmarking app with:
- URL metadata extraction (OG/Twitter meta, oEmbed fallback)
- Image caching in Postgres with 480px thumbnails
- Multi-tag filtering with Ctrl/Cmd for OR mode
- Fuzzy tag suggestions and inline tag editing
- Browser console auth() with first-use password setup
- Brutalist UI with Commit Mono font and Pico CSS
- Light/dark mode via browser preference

vendor/github.com/jackc/pgx/v5/pgproto3/cancel_request.go

@@ -0,0 +1,58 @@
+package pgproto3
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"errors"
+
+	"github.com/jackc/pgx/v5/internal/pgio"
+)
+
+const cancelRequestCode = 80877102
+
+type CancelRequest struct {
+	ProcessID uint32
+	SecretKey uint32
+}
+
+// Frontend identifies this message as sendable by a PostgreSQL frontend.
+func (*CancelRequest) Frontend() {}
+
+func (dst *CancelRequest) Decode(src []byte) error {
+	if len(src) != 12 {
+		return errors.New("bad cancel request size")
+	}
+
+	requestCode := binary.BigEndian.Uint32(src)
+
+	if requestCode != cancelRequestCode {
+		return errors.New("bad cancel request code")
+	}
+
+	dst.ProcessID = binary.BigEndian.Uint32(src[4:])
+	dst.SecretKey = binary.BigEndian.Uint32(src[8:])
+
+	return nil
+}
+
+// Encode encodes src into dst. dst will include the 4 byte message length.
+func (src *CancelRequest) Encode(dst []byte) ([]byte, error) {
+	dst = pgio.AppendInt32(dst, 16)
+	dst = pgio.AppendInt32(dst, cancelRequestCode)
+	dst = pgio.AppendUint32(dst, src.ProcessID)
+	dst = pgio.AppendUint32(dst, src.SecretKey)
+	return dst, nil
+}
+
+// MarshalJSON implements encoding/json.Marshaler.
+func (src CancelRequest) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type      string
+		ProcessID uint32
+		SecretKey uint32
+	}{
+		Type:      "CancelRequest",
+		ProcessID: src.ProcessID,
+		SecretKey: src.SecretKey,
+	})
+}