Devlog-Seite: Bildergalerie, Projekt-Chips, Monats-Trenner

- Bild-Attachments werden beim Archivieren lokal gespeichert (Discord-CDN-URLs
  laufen ab) und unter /devlog-assets/ ausgeliefert; DB-Migration: images-Spalte
- Frontend: Bildergalerie im Grid (responsive nach Anzahl), Embed-Titel als
  Projekt-Chip, Commit-Fußzeile abgesetzt, Monats-Trenner in der Timeline
- Backfill lädt Bilder alter Devlogs nach (Dedupe verhindert Doppel-Downloads)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/db.js

@@ -35,6 +35,12 @@ db.exec(`
     CREATE INDEX IF NOT EXISTS idx_devlogs_posted ON devlogs (posted_at DESC);
 `);
 
+// Migration: images-Spalte (JSON-Array lokaler Dateinamen) für bestehende DBs
+const devlogCols = db.prepare('PRAGMA table_info(devlogs)').all();
+if (!devlogCols.some((c) => c.name === 'images')) {
+    db.exec(`ALTER TABLE devlogs ADD COLUMN images TEXT NOT NULL DEFAULT '[]'`);
+}
+
 const insertCommit = db.prepare(`
     INSERT OR IGNORE INTO commits (sha, repo, branch, message, author_name, author_user, url, committed_at)
     VALUES (@sha, @repo, @branch, @message, @author_name, @author_user, @url, @committed_at)
@@ -50,19 +56,25 @@ export const saveCommits = db.transaction((commits) => {
 });
 
 const insertDevlog = db.prepare(`
-    INSERT OR IGNORE INTO devlogs (message_id, channel_id, content, author_name, posted_at)
-    VALUES (@message_id, @channel_id, @content, @author_name, @posted_at)
+    INSERT OR IGNORE INTO devlogs (message_id, channel_id, content, author_name, posted_at, images)
+    VALUES (@message_id, @channel_id, @content, @author_name, @posted_at, @images)
 `);
+const hasDevlogStmt = db.prepare('SELECT 1 FROM devlogs WHERE message_id = ?');
 
 /** Devlog speichern — bereits bekannte Message-IDs werden ignoriert. Gibt true zurück, wenn neu. */
 export function saveDevlog(devlog) {
-    return insertDevlog.run(devlog).changes > 0;
+    return insertDevlog.run({ images: '[]', ...devlog }).changes > 0;
+}
+
+/** true, wenn die Message schon archiviert ist (spart z. B. erneute Bild-Downloads) */
+export function hasDevlog(messageId) {
+    return Boolean(hasDevlogStmt.get(messageId));
 }
 
 // --- Lese-Queries für die Web-API (Feature 4) ---
 
 const selectDevlogs = db.prepare(`
-    SELECT message_id, content, author_name, posted_at
+    SELECT message_id, content, author_name, posted_at, images
     FROM devlogs ORDER BY posted_at DESC LIMIT ? OFFSET ?
 `);
 const countDevlogsStmt = db.prepare('SELECT COUNT(*) AS n FROM devlogs');