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>

frontend/src/pages/Changelog.jsx

@@ -0,0 +1,76 @@
+import { useEffect, useState } from 'react';
+import { apiGet } from '../api.js';
+import { Markdown } from '../markdown.jsx';
+
+const dateFmt = new Intl.DateTimeFormat('de-DE', {
+    day: '2-digit', month: 'long', year: 'numeric',
+});
+
+export default function Changelog() {
+    const [data, setData] = useState(null);
+    const [page, setPage] = useState(1);
+    const [error, setError] = useState(false);
+
+    useEffect(() => {
+        setError(false);
+        apiGet(`/api/releases?page=${page}`).then(setData).catch(() => setError(true));
+        window.scrollTo(0, 0);
+    }, [page]);
+
+    const pages = data ? Math.ceil(data.total / data.pageSize) : 0;
+
+    return (
+        <>
+            <section className="page-header">
+                <div className="page-bg-text">CHANGELOG</div>
+                <div className="page-header-grid" aria-hidden="true" />
+                <div className="page-header-content">
+                    <div className="page-tag">// Releases</div>
+                    <h1 className="page-title">Changelog</h1>
+                    <p className="page-subtitle">Alle Versionen und Release-Notes.</p>
+                </div>
+            </section>
+
+            <section className="content">
+                {error && <p className="notice">Changelog konnte nicht geladen werden.</p>}
+                {!error && !data && <p className="notice">Lade …</p>}
+                {data?.total === 0 && <p className="notice">Noch keine Releases veröffentlicht.</p>}
+
+                {data?.total > 0 &&
+                    data.items.map((r) => (
+                        <article className="card release-card" key={`${r.repo}/${r.tag}`}>
+                            <div className="card-meta">
+                                <span className="release-tag">{r.tag}</span>
+                                {r.prerelease ? <span className="chip chip-branch">Pre-Release</span> : null}
+                                <span className="chip chip-repo">{r.repo.split('/').pop()}</span>
+                                <span className="card-rel">{dateFmt.format(new Date(r.published_at))}</span>
+                            </div>
+                            {r.name && r.name !== r.tag && <h3 className="release-name">{r.name}</h3>}
+                            <div className="card-body">
+                                <Markdown text={r.body || '*Keine Release-Notes.*'} />
+                            </div>
+                            {r.url && (
+                                <div className="card-footer">
+                                    <a href={r.url} target="_blank" rel="noreferrer">Release in Gitea ansehen →</a>
+                                </div>
+                            )}
+                        </article>
+                    ))}
+
+                {pages > 1 && (
+                    <div className="pager">
+                        <button className="btn" disabled={page <= 1} onClick={() => setPage(page - 1)}>
+                            ← Neuere
+                        </button>
+                        <span className="pager-info">
+                            {String(page).padStart(2, '0')} / {String(pages).padStart(2, '0')}
+                        </span>
+                        <button className="btn" disabled={page >= pages} onClick={() => setPage(page + 1)}>
+                            Ältere →
+                        </button>
+                    </div>
+                )}
+            </section>
+        </>
+    );
+}

frontend/src/pages/Settings.jsx

@@ -136,6 +136,20 @@ export default function Settings({ me }) {
                             <button className="btn" onClick={() => sendTest('commit')}>Test senden</button>
                         </div>
                     </div>
+
+                    <div className="field">
+                        <label>Release-Kanal <span className="field-hint">Ankündigungen bei neuen Gitea-Releases — leer = aus</span></label>
+                        <div className="field-row">
+                            <select
+                                value={form.release_channel_id ?? ''}
+                                onChange={(e) => setForm({ ...form, release_channel_id: e.target.value })}
+                            >
+                                <option value="">— deaktiviert —</option>
+                                {channelOptions}
+                            </select>
+                            <button className="btn" onClick={() => sendTest('release')}>Test senden</button>
+                        </div>
+                    </div>
                 </div>
 
                 {/* Commit-Feed */}