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

internal/services/dashboard_service.go

@@ -405,10 +405,10 @@ func (s *DashboardService) RestoreSystemCollection(ctx context.Context, userID u
 		Priority    int32
 		QueryType   string
 	}{
-		"continue-reading": {"Books you're currently reading (0 < progress < 1)", "📖", "#7aa2f7", 1, "continue-reading"},
-		"recently-added":   {"Newly added items to this library", "🆕", "#9ece6a", 2, "recently-added"},
-		"recently-read":    {"Books you've finished (progress >= 1)", "✅", "#e0af68", 3, "recently-read"},
-		"not-started":      {"Books you haven't read yet (progress = 0 or no record)", "📕", "#f7768e", 4, "not-started"},
+		"Continue Reading": {"Books you're currently reading (0 < progress < 1)", "📖", "#7aa2f7", 1, "continue-reading"},
+		"Recently Added":   {"Newly added items to this library", "🆕", "#9ece6a", 2, "recently-added"},
+		"Recently Read":    {"Books you've finished (progress >= 1)", "✅", "#e0af68", 3, "recently-read"},
+		"Not Started":      {"Books you haven't read yet (progress = 0 or no record)", "📕", "#f7768e", 4, "not-started"},
 	}
 
 	meta, exists := defaultMetadata[collectionName]