Add pagination to QSO Log and back buttons to pages

- Add backend pagination support for /api/qsos endpoint (page, limit params)
- Return paginated results with metadata (totalCount, totalPages, hasNext, hasPrev)
- Add pagination UI to QSOs page with prev/next buttons and page numbers
- Add back button to QSO Log and Settings pages linking to main menu
- Reset to page 1 when applying filters

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/backend/index.js

@@ -391,6 +391,7 @@ const app = new Elysia()
   /**
    * GET /api/qsos
    * Get user's QSOs (requires authentication)
+   * Supports pagination: ?page=1&limit=100
    */
   .get('/api/qsos', async ({ user, query, set }) => {
     if (!user) {
@@ -404,12 +405,17 @@ const app = new Elysia()
       if (query.mode) filters.mode = query.mode;
       if (query.confirmed) filters.confirmed = query.confirmed === 'true';
 
-      const qsos = await getUserQSOs(user.id, filters);
+      // Pagination options
+      const options = {
+        page: query.page ? parseInt(query.page) : 1,
+        limit: query.limit ? parseInt(query.limit) : 100,
+      };
+
+      const result = await getUserQSOs(user.id, filters, options);
 
       return {
         success: true,
-        qsos,
-        count: qsos.length,
+        ...result,
       };
     } catch (error) {
       set.status = 500;