Öffentliche Roadmap-Seite aus Gitea-Milestones

- GET /api/roadmap (public): Milestones des Setting roadmap_repo, 5-min-Cache,
  letzter guter Stand als Fallback bei Gitea-Ausfall
- /roadmap: Gruppen In Arbeit / Geplant / Fertig, Fortschrittsbalken im Brand-Look,
  Ziel-Monat, Markdown-Beschreibungen; Nav-Link öffentlich
- Setup-Seite: Roadmap-Repo konfigurierbar

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

frontend/src/style.css

@@ -398,6 +398,35 @@ body::after {
 .card-footer a { color: var(--muted); border-bottom: 1px solid transparent; }
 .card-footer a:hover { color: var(--neon); }
 
+/* ── ROADMAP ───────────────────────────────────────── */
+.roadmap-group { margin-bottom: 2.25rem; }
+.roadmap-group .settings-title { margin-bottom: 1rem; }
+.milestone { margin-bottom: 1.1rem; }
+.milestone-title {
+    font-family: var(--display);
+    font-size: 1.3rem; letter-spacing: .04em;
+    color: var(--text);
+}
+.progress {
+    height: 6px;
+    background: rgba(255, 255, 255, .06);
+    margin-top: .8rem;
+    overflow: hidden;
+}
+.progress-bar {
+    height: 100%;
+    background: linear-gradient(90deg, var(--neon2), var(--neon));
+    box-shadow: 0 0 10px rgba(245, 197, 24, .4);
+    transition: width .6s ease;
+}
+.progress-info {
+    display: flex; justify-content: space-between;
+    font-family: var(--mono);
+    font-size: .65rem; letter-spacing: .1em;
+    color: var(--muted2);
+    margin-top: .35rem;
+}
+
 /* ── CHANGELOG ─────────────────────────────────────── */
 .release-card { margin-bottom: 1.5rem; }
 .release-tag {