Per-user podcasts, file uploads, RSS images, Docker support

- Each user owns a podcast: podcast title/author/image on users table
- Episodes scoped by user_id with context-based auth
- Audio file upload replaces URL linking, served from /uploads/
- Podcast and per-episode images with itunes:image in RSS
- RSS per-user via ?user=N, dashboard shows user-specific feed URL
- Settings form for title + author + image per user
- Docker multi-stage build (golang:1.25-alpine / alpine:3.21)
- Removed PODSTALK_TITLE/AUTHOR env vars

template/dashboard.html

@@ -40,6 +40,11 @@
                         <input type="text" id="podcast_title" name="podcast_title" class="nb-input blue"
                             value="{{.PodcastTitle}}" />
                     </div>
+                    <div class="form-group" style="flex: 1; min-width: 200px;">
+                        <label for="podcast_author">Author</label>
+                        <input type="text" id="podcast_author" name="podcast_author" class="nb-input blue"
+                            value="{{.PodcastAuthor}}" placeholder="Podcast Host" />
+                    </div>
                     <div class="form-group">
                         <label for="podcast_image">Podcast Image</label>
                         <input type="file" id="podcast_image" name="podcast_image" accept="image/*" />
@@ -66,7 +71,7 @@
             </div>
         </div>
         <script>
-            const rssURL = '{{.BaseURL}}/rss';
+            const rssURL = '{{.BaseURL}}/rss?user={{.UserID}}';
             document.getElementById('rss-url').textContent = rssURL;
             function copyRSS() {
                 navigator.clipboard.writeText(rssURL).then(() => {