feat: Notifications page, Sidebar layout fixes, and Achievements enhancements

- implemented /notifications page with overdue/upcoming alerts
- Fixed sidebar scrolling in collapsed mode
- Moved notification button to sidebar footer
- Enhanced Achievements page with streak stats and tooltips
- Improved XP history to show task titles
- Added missing translations (en/de)
- Removed top bar header
- Fixed Docker environment routing

shared/gamification.ts

@@ -8,7 +8,17 @@ export const LEVEL_THRESHOLDS = [
     3500,   // Level 7: 3500-4999
     5000,   // Level 8: 5000-7499
     7500,   // Level 9: 7500-9999
-    10000   // Level 10: 10000+
+    10000,  // Level 10: 10000-14999
+    15000,  // Level 11: 15000-24999
+    25000,  // Level 12: 25000-39999
+    40000,  // Level 13: 40000-59999
+    60000,  // Level 14: 60000-84999
+    85000,  // Level 15: 85000-119999
+    120000, // Level 16: 120000-159999
+    160000, // Level 17: 160000-209999
+    210000, // Level 18: 210000-269999
+    270000, // Level 19: 270000-349999
+    350000  // Level 20: 350000+
 ];
 
 export function getLevelFromXP(xp: number): number {
@@ -48,7 +58,17 @@ export const RANK_KEYS = [
     'grandmaster',  // Level 7
     'virtuoso',     // Level 8
     'legend',       // Level 9
-    'mythic'        // Level 10
+    'mythic',       // Level 10
+    'titan',        // Level 11
+    'sentinel',     // Level 12
+    'vanguard',     // Level 13
+    'oracle',       // Level 14
+    'ascendant',    // Level 15
+    'ethereal',     // Level 16
+    'celestial',    // Level 17
+    'divine',       // Level 18
+    'omnipotent',   // Level 19
+    'eternal'       // Level 20
 ];
 
 export function getRankKey(level: number): string {