Slug-based RSS URLs and success flash messages

- Add podcast_slug to users with global uniqueness check
- RSS available at /rss/{slug} (path-based) with legacy ?slug= fallback
- Slug field in dashboard settings with validation (lowercase, hyphens)
- JS flash messages for success/error after form submissions
- Remove unused imports

store/store.go

@@ -12,6 +12,7 @@ type User struct {
 	Email         string
 	PasswordHash  string
 	PodcastTitle  string
+	PodcastSlug   string
 	PodcastImage  string
 	PodcastAuthor string
 	CreatedAt     time.Time
@@ -53,6 +54,7 @@ func migrate(db *sql.DB) error {
 		email TEXT NOT NULL UNIQUE,
 		password_hash TEXT NOT NULL,
 		podcast_title TEXT NOT NULL DEFAULT '',
+		podcast_slug TEXT NOT NULL DEFAULT '',
 		podcast_image TEXT NOT NULL DEFAULT '',
 		podcast_author TEXT NOT NULL DEFAULT '',
 		created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
@@ -95,8 +97,8 @@ func (s *Store) CreateUser(email, passwordHash string) (int64, error) {
 
 func (s *Store) UserByEmail(email string) (*User, error) {
 	u := &User{}
-	err := s.db.QueryRow("SELECT id, email, password_hash, podcast_title, podcast_image, podcast_author, created_at FROM users WHERE email = ?", email).
-		Scan(&u.ID, &u.Email, &u.PasswordHash, &u.PodcastTitle, &u.PodcastImage, &u.PodcastAuthor, &u.CreatedAt)
+	err := s.db.QueryRow("SELECT id, email, password_hash, podcast_title, podcast_slug, podcast_image, podcast_author, created_at FROM users WHERE email = ?", email).
+		Scan(&u.ID, &u.Email, &u.PasswordHash, &u.PodcastTitle, &u.PodcastSlug, &u.PodcastImage, &u.PodcastAuthor, &u.CreatedAt)
 	if err != nil {
 		return nil, err
 	}
@@ -105,17 +107,39 @@ func (s *Store) UserByEmail(email string) (*User, error) {
 
 func (s *Store) GetUser(id int64) (*User, error) {
 	u := &User{}
-	err := s.db.QueryRow("SELECT id, email, password_hash, podcast_title, podcast_image, podcast_author, created_at FROM users WHERE id = ?", id).
-		Scan(&u.ID, &u.Email, &u.PasswordHash, &u.PodcastTitle, &u.PodcastImage, &u.PodcastAuthor, &u.CreatedAt)
+	err := s.db.QueryRow("SELECT id, email, password_hash, podcast_title, podcast_slug, podcast_image, podcast_author, created_at FROM users WHERE id = ?", id).
+		Scan(&u.ID, &u.Email, &u.PasswordHash, &u.PodcastTitle, &u.PodcastSlug, &u.PodcastImage, &u.PodcastAuthor, &u.CreatedAt)
 	if err != nil {
 		return nil, err
 	}
 	return u, nil
 }
 
-func (s *Store) UpdateUserPodcast(id int64, title, image, author string) error {
-	_, err := s.db.Exec("UPDATE users SET podcast_title=?, podcast_image=?, podcast_author=? WHERE id=?",
-		title, image, author, id)
+func (s *Store) UserBySlug(slug string) (*User, error) {
+	u := &User{}
+	err := s.db.QueryRow("SELECT id, email, password_hash, podcast_title, podcast_slug, podcast_image, podcast_author, created_at FROM users WHERE podcast_slug = ?", slug).
+		Scan(&u.ID, &u.Email, &u.PasswordHash, &u.PodcastTitle, &u.PodcastSlug, &u.PodcastImage, &u.PodcastAuthor, &u.CreatedAt)
+	if err != nil {
+		return nil, err
+	}
+	return u, nil
+}
+
+func (s *Store) SlugTaken(slug string, excludeUserID int64) (bool, error) {
+	var id int64
+	err := s.db.QueryRow("SELECT id FROM users WHERE podcast_slug = ? AND id != ?", slug, excludeUserID).Scan(&id)
+	if err == sql.ErrNoRows {
+		return false, nil
+	}
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+func (s *Store) UpdateUserPodcast(id int64, title, slug, image, author string) error {
+	_, err := s.db.Exec("UPDATE users SET podcast_title=?, podcast_slug=?, podcast_image=?, podcast_author=? WHERE id=?",
+		title, slug, image, author, id)
 	return err
 }