fix: address PR #1641 review comments (round 2)

- Remove duplicate TranscriptWatcher/config imports in worker-service.ts
- Use normalizePlatformSource in handleSessionInitByClaudeId for consistency
- Don't skip DB completion when session not in memory (completeByClaudeId)
- Add try-catch around fetch in useContextPreview refresh callback
- Deduplicate store.getAllProjects() call in DataRoutes
- Fix malformed comment separators in migration runner
- Fix missing closing brace and JSDoc opener (merge artifact) in migration runner

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ui/viewer/hooks/useContextPreview.ts

@@ -96,12 +96,16 @@ export function useContextPreview(settings: Settings): UseContextPreviewResult {
       params.append('platformSource', selectedSource);
     }
 
-    const response = await fetch(`/api/context/preview?${params}`);
-    const text = await response.text();
+    try {
+      const response = await fetch(`/api/context/preview?${params}`);
+      const text = await response.text();
 
-    if (response.ok) {
-      setPreview(text);
-    } else {
+      if (response.ok) {
+        setPreview(text);
+      } else {
+        setError('Failed to load preview');
+      }
+    } catch {
       setError('Failed to load preview');
     }