feat: add database models and queries for annotations

- Add MediaNotes and MediaHighlights model structs with pgx v5 types
- Add EbookNotes and EbookHighlights for backward compatibility
- Add complete CRUD SQL queries for notes and highlights
- Add database connection pool function using pgx v5
- Generate sqlc code for new annotation functionality

internal/database/db.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 type DBTX interface {
@@ -30,3 +31,8 @@ func (q *Queries) WithTx(tx pgx.Tx) *Queries {
 		db: tx,
 	}
 }
+
+// NewConnection creates a new database connection pool
+func NewConnection(databaseURL string) (*pgxpool.Pool, error) {
+	return pgxpool.New(context.Background(), databaseURL)
+}