feat: Tutorial-Fortschritt serverseitig persistieren (Resume/Restart)

- Neuer Router /api/tutorial mit GET/PUT/DELETE für Fortschritt pro User
- DB-Migration: tutorial_step + tutorial_completed in users-Tabelle
- Resume-Dialog bei abgebrochenem Tutorial (Fortsetzen/Neu starten)
- Chat-Hinweis passt sich dem Tutorial-Status dynamisch an
- API-Methoden: getTutorialState, saveTutorialState, resetTutorialState

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/static/js/api.js

@@ -215,6 +215,19 @@ const API = {
     },
 
     // Export
+
+    // Tutorial-Fortschritt
+    getTutorialState() {
+        return this._request('GET', '/tutorial/state');
+    },
+
+    saveTutorialState(data) {
+        return this._request('PUT', '/tutorial/state', data);
+    },
+
+    resetTutorialState() {
+        return this._request('DELETE', '/tutorial/state');
+    },
     exportIncident(id, format, scope) {
         const token = localStorage.getItem('osint_token');
         return fetch(`${this.baseUrl}/incidents/${id}/export?format=${format}&scope=${scope}`, {