migrate to SQLite and prepare for MCP deployment

Switch from PostgreSQL to SQLite (modernc.org/sqlite, pure Go) for
simpler deployment on the MCP platform. Fix URL normalization to
preserve query parameters so sites like YouTube deduplicate correctly.
Add Dockerfile, Makefile, and MCP service definition. Add pg2sqlite
migration tool. Support $PORT env var for MCP port assignment.

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

links/url.go

@@ -2,17 +2,16 @@ package links
 
 import (
 	"context"
+	"database/sql"
 	"log"
 	"net/url"
 	"time"
 
 	"github.com/Masterminds/squirrel"
 	"github.com/google/uuid"
-	"github.com/jackc/pgx/v4"
-	"github.com/jackc/pgx/v4/pgxpool"
 )
 
-var psql = squirrel.StatementBuilder.PlaceholderFormat(squirrel.Dollar)
+var sq = squirrel.StatementBuilder.PlaceholderFormat(squirrel.Question)
 
 type URL struct {
 	ID        string
@@ -26,26 +25,27 @@ func (u *URL) Timestamp() string {
 	return u.CreatedAt.Format("2006-01-02 15:04")
 }
 
-func (u *URL) Store(ctx context.Context, db *pgxpool.Pool) error {
-	stmt := psql.Insert("urls").
+func (u *URL) Store(ctx context.Context, db *sql.DB) error {
+	stmt := sq.Insert("urls").
 		Columns("id", "url", "nurl", "short", "created_at").
-		Values(u.ID, u.URL, u.NURL, u.Short, u.CreatedAt)
+		Values(u.ID, u.URL, u.NURL, u.Short, u.CreatedAt.Format(time.RFC3339))
 	query, args, err := stmt.ToSql()
 	if err != nil {
 		return err
 	}
 
-	_, err = db.Exec(ctx, query, args...)
+	_, err = db.ExecContext(ctx, query, args...)
 	return err
 }
 
 // Normalize cleans the URL to only the parts we care about.
 func Normalize(u *url.URL) *url.URL {
 	norm := &url.URL{
-		Scheme:  u.Scheme,
-		Host:    u.Host,
-		Path:    u.Path,
-		RawPath: u.RawPath,
+		Scheme:   u.Scheme,
+		Host:     u.Host,
+		Path:     u.Path,
+		RawPath:  u.RawPath,
+		RawQuery: u.RawQuery,
 	}
 	return norm
 }
@@ -61,18 +61,19 @@ func NormalizeString(s string) (string, error) {
 }
 
 // Clean should scrub out junk from the URL.
-func Clean(u *url.URL, keepQuery bool) *url.URL {
+func Clean(u *url.URL, stripQuery bool) *url.URL {
 	norm := &url.URL{
 		Scheme:      u.Scheme,
 		Host:        u.Host,
 		Path:        u.Path,
 		RawPath:     u.RawPath,
+		RawQuery:    u.RawQuery,
 		Fragment:    u.Fragment,
 		RawFragment: u.RawFragment,
 	}
 
-	if keepQuery {
-		norm.RawQuery = u.RawQuery
+	if stripQuery {
+		norm.RawQuery = ""
 	}
 	return norm
 }
@@ -107,7 +108,7 @@ func FromString(s string) (*URL, error) {
 	return New(u), nil
 }
 
-func Lookup(ctx context.Context, db *pgxpool.Pool, s string) (string, error) {
+func Lookup(ctx context.Context, db *sql.DB, s string) (string, error) {
 	u, err := url.Parse(s)
 	if err != nil {
 		return "", nil
@@ -115,14 +116,14 @@ func Lookup(ctx context.Context, db *pgxpool.Pool, s string) (string, error) {
 
 	u = Normalize(u)
 
-	stmt := psql.Select("short").From("urls").
+	stmt := sq.Select("short").From("urls").
 		Where(squirrel.Eq{"nurl": u.String()})
 	query, args, err := stmt.ToSql()
 	if err != nil {
 		return "", err
 	}
 
-	row := db.QueryRow(ctx, query, args...)
+	row := db.QueryRowContext(ctx, query, args...)
 
 	var short string
 	err = row.Scan(&short)
@@ -133,13 +134,13 @@ func Lookup(ctx context.Context, db *pgxpool.Pool, s string) (string, error) {
 	return short, nil
 }
 
-func StoreURL(ctx context.Context, db *pgxpool.Pool, s string) (string, error) {
+func StoreURL(ctx context.Context, db *sql.DB, s string) (string, error) {
 	short, err := Lookup(ctx, db, s)
 	if err == nil {
 		return short, nil
 	}
 
-	if err != pgx.ErrNoRows {
+	if err != sql.ErrNoRows {
 		return "", err
 	}
 
@@ -156,48 +157,50 @@ func StoreURL(ctx context.Context, db *pgxpool.Pool, s string) (string, error) {
 	return u.Short, nil
 }
 
-func RetrieveURL(ctx context.Context, db *pgxpool.Pool, short string) (string, error) {
+func RetrieveURL(ctx context.Context, db *sql.DB, short string) (string, error) {
 	log.Printf("look up url for short code %s", short)
-	stmt := psql.Select("url").From("urls").
+	stmt := sq.Select("url").From("urls").
 		Where(squirrel.Eq{"short": short})
 	query, args, err := stmt.ToSql()
 	if err != nil {
 		return "", err
 	}
 
-	row := db.QueryRow(ctx, query, args...)
-	var url string
+	row := db.QueryRowContext(ctx, query, args...)
+	var u string
 
-	err = row.Scan(&url)
+	err = row.Scan(&u)
 	if err != nil {
 		return "", err
 	}
 
-	return url, nil
+	return u, nil
 }
 
-func FetchAll(ctx context.Context, db *pgxpool.Pool) ([]*URL, error) {
-	stmt := psql.Select("*").From("urls").OrderBy("created_at")
+func FetchAll(ctx context.Context, db *sql.DB) ([]*URL, error) {
+	stmt := sq.Select("id", "url", "nurl", "short", "created_at").
+		From("urls").OrderBy("created_at")
 	query, args, err := stmt.ToSql()
 	if err != nil {
 		return nil, err
 	}
 
-	rows, err := db.Query(ctx, query, args...)
+	rows, err := db.QueryContext(ctx, query, args...)
 	if err != nil {
 		return nil, err
 	}
+	defer rows.Close()
 
 	var urls []*URL
 	for rows.Next() {
 		u := &URL{}
-		err = rows.Scan(
-			&u.ID,
-			&u.URL,
-			&u.NURL,
-			&u.Short,
-			&u.CreatedAt,
-		)
+		var ts string
+		err = rows.Scan(&u.ID, &u.URL, &u.NURL, &u.Short, &ts)
+		if err != nil {
+			return nil, err
+		}
+
+		u.CreatedAt, err = time.Parse(time.RFC3339, ts)
 		if err != nil {
 			return nil, err
 		}