fix(seo): comprehensive SEO improvements per expert audit

- Add public/robots.txt (allow all, disallow /admin and /login, reference sitemap)
- Add public/sitemap.xml (5 public routes with change frequencies and priorities)
- Fix heading hierarchy: h2 -> h1 on about, schedule, events, contact pages
- Remove dead footer href="#" links:
  - Volunteer/Corporate Giving/Planned Giving -> routerLink to /contact with subject query param
  - Social media links -> conditional on config().social_* fields (hidden when empty)
- Fix logo ARIA: add aria-hidden="true" to decorative logo in about page divider
- Add social_facebook, social_twitter, social_instagram, social_youtube to:
  - StationConfig DB model + startup migration
  - StationConfigResponse and StationConfigUpdate schemas
  - Frontend StationConfig TypeScript interface
- Fix events "Learn More" dead link -> routerLink to /contact

src/app/footer/footer.component.html

@@ -35,18 +35,26 @@
             @if (config().donation_url) {
             <li><a [href]="config().donation_url" target="_blank" rel="noopener noreferrer">Become a Member</a></li>
             }
-            <li><a href="#">Volunteer</a></li>
-            <li><a href="#">Corporate Giving</a></li>
-            <li><a href="#">Planned Giving</a></li>
+            <li><a routerLink="/contact" [queryParams]="{subject: 'volunteer'}">Volunteer</a></li>
+            <li><a routerLink="/contact" [queryParams]="{subject: 'advertising'}">Corporate Giving</a></li>
+            <li><a routerLink="/contact" [queryParams]="{subject: 'general'}">Planned Giving</a></li>
           </ul>
         </div>
         <div class="footer-col">
           <h4>Follow Us</h4>
           <div class="social-links">
-            <a href="#" aria-label="Facebook" class="social-link">📘</a>
-            <a href="#" aria-label="Twitter" class="social-link">🐦</a>
-            <a href="#" aria-label="Instagram" class="social-link">📷</a>
-            <a href="#" aria-label="YouTube" class="social-link">📺</a>
+            @if (config().social_facebook) {
+            <a [href]="config().social_facebook" target="_blank" rel="noopener noreferrer" aria-label="Facebook" class="social-link">📘</a>
+            }
+            @if (config().social_twitter) {
+            <a [href]="config().social_twitter" target="_blank" rel="noopener noreferrer" aria-label="Twitter" class="social-link">🐦</a>
+            }
+            @if (config().social_instagram) {
+            <a [href]="config().social_instagram" target="_blank" rel="noopener noreferrer" aria-label="Instagram" class="social-link">📷</a>
+            }
+            @if (config().social_youtube) {
+            <a [href]="config().social_youtube" target="_blank" rel="noopener noreferrer" aria-label="YouTube" class="social-link">📺</a>
+            }
           </div>
         </div>
       </div>