v1.3.2: SEO fixes + map bugfixes

SEO:
- Landing page converted to Server Component (SSR)
- Extracted NavAuthButtons + ContactForm as client islands
- Removed fake aggregateRating from JSON-LD
- Added FAQPage JSON-LD schema (7 questions)
- Extended sitemap: /datenschutz, /spenden, /demo

Map fixes:
- WebGL context lost recovery (black tiles after inactivity)
- Page visibility handler for tile reload on tab switch
- Arrow direction: geographic bearing instead of screen angle
- All markers rotationAlignment viewport->map (geographic orientation)
- DEL key now deletes selected lines/polygons/arrows (not just symbols)
- Default drawing color: black

src/stores/tool-store.ts

@@ -21,7 +21,7 @@ interface ToolStore {
 
 export const useToolStore = create<ToolStore>((set) => ({
   activeTool: 'select',
-  activeColor: '#ff0000', // Default Rot
+  activeColor: '#000000', // Default Schwarz
   lineType: 'solid',
   lineWidth: 3,
   selectedFeatureId: null,