Update default system collection names to Title Case format

Changed the 4 default system collection names from kebab-case to Title Case
with spaces for better readability and professional appearance:

Changes:
- "continue-reading" → "Continue Reading"
- "recently-added" → "Recently Added"
- "recently-read" → "Recently Read"
- "not-started" → "Not Started"

Implementation details:
- Collection Name field: Updated to Title Case (user-visible identifier)
- QueryType field: Unchanged, remains kebab-case (internal switch/case logic)
- All map keys updated to use new Title Case names as lookups
- Restore modal option values updated to match new names

Files modified:
- internal/handlers/auth.go: Default collection creation for new users
- internal/handlers/dashboard.go: Restore endpoint validation map
- internal/services/dashboard_service.go: System collection metadata map
- templates/restore_system_collection_modal.templ: Form option values

Benefits:
- Cleaner, more professional display names for end users
- Consistent with existing restore modal UI labels
- Improved user experience with properly formatted collection names
- Internal QueryType identifiers remain unchanged for code logic

templates/restore_system_collection_modal.templ

@@ -15,10 +15,10 @@ templ RestoreSystemCollectionModal() {
 				>
 					<select name="collection_name" class="w-full px-4 py-2 border rounded-lg" style="background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);">
 						<option value="">Select collection...</option>
-						<option value="continue-reading">Continue Reading</option>
-						<option value="recently-added">Recently Added</option>
-						<option value="recently-read">Recently Read</option>
-						<option value="not-started">Not Started</option>
+						<option value="Continue Reading">Continue Reading</option>
+						<option value="Recently Added">Recently Added</option>
+						<option value="Recently Read">Recently Read</option>
+						<option value="Not Started">Not Started</option>
 					</select>
 					<div class="flex justify-end space-x-3 mt-6">
 						<button type="button" @click="closeCollectionModal()" class="btn-secondary px-4 py-2 rounded-lg">Cancel</button>