Release-Ankündigungen + öffentliche Changelog-Seite

- Gitea-Release-Webhook: Releases werden archiviert (releases-Tabelle) und neue
  'published'-Releases als oranges 🚀-Embed mit Buttons angekündigt
- Release-Kanal auf der Setup-Seite wählbar (leer = Feature aus) + Test-Button
- /changelog: öffentliche Seite mit Tag-Chips, Pre-Release-Badge, Release-Notes
- /api/releases öffentlich; Updates/Redeliveries posten nicht doppelt

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

src/db.js

@@ -41,6 +41,20 @@ if (!devlogCols.some((c) => c.name === 'images')) {
     db.exec(`ALTER TABLE devlogs ADD COLUMN images TEXT NOT NULL DEFAULT '[]'`);
 }
 
+// Releases (Gitea-Release-Webhook) — für Ankündigungen + Changelog-Seite
+db.exec(`
+    CREATE TABLE IF NOT EXISTS releases (
+        repo         TEXT NOT NULL,
+        tag          TEXT NOT NULL,
+        name         TEXT,
+        body         TEXT,
+        url          TEXT,
+        prerelease   INTEGER NOT NULL DEFAULT 0,
+        published_at TEXT NOT NULL,
+        PRIMARY KEY (repo, tag)
+    );
+`);
+
 // Volltextsuche (FTS5) über Devlogs — Trigger halten den Index synchron
 db.exec(`
     CREATE VIRTUAL TABLE IF NOT EXISTS devlogs_fts USING fts5(content, message_id UNINDEXED);
@@ -170,6 +184,33 @@ export function listCommits(limit, offset) {
     return { items: selectCommits.all(limit, offset), total: countCommitsStmt.get().n };
 }
 
+const upsertRelease = db.prepare(`
+    INSERT INTO releases (repo, tag, name, body, url, prerelease, published_at)
+    VALUES (@repo, @tag, @name, @body, @url, @prerelease, @published_at)
+    ON CONFLICT(repo, tag) DO UPDATE SET
+        name = excluded.name, body = excluded.body, url = excluded.url,
+        prerelease = excluded.prerelease
+`);
+
+/** Release speichern/aktualisieren. Gibt true zurück, wenn neu (→ ankündigen). */
+export function saveRelease(release) {
+    const existed = db
+        .prepare('SELECT 1 FROM releases WHERE repo = ? AND tag = ?')
+        .get(release.repo, release.tag);
+    upsertRelease.run(release);
+    return !existed;
+}
+
+const selectReleases = db.prepare(`
+    SELECT repo, tag, name, body, url, prerelease, published_at
+    FROM releases ORDER BY published_at DESC LIMIT ? OFFSET ?
+`);
+const countReleasesStmt = db.prepare('SELECT count(*) AS n FROM releases');
+
+export function listReleases(limit, offset) {
+    return { items: selectReleases.all(limit, offset), total: countReleasesStmt.get().n };
+}
+
 /** Statistiken fürs Status-Panel der Settings-Seite */
 export function archiveStats() {
     return {