Frontend error handling & cleanup

[bbethell-1]

Findings

SSE JSON.parse without try/catch (High)

• src/frontend/src/hooks/useJobStream.ts line 55: Malformed SSE data crashes the event handler silently.

Multiple unhandled async errors in BrowsePage (High)

• src/frontend/src/pages/BrowsePage.tsx: handleAnalyze, handleAddTag, handleRemoveTag, handleSaveNote, handleSetContentPath, handleOverrideUrl, handleSetDuration, handleFlag — none have try/catch.

Polling timer not cleaned up on unmount (High)

• src/frontend/src/pages/BrowsePage.tsx lines 271-287: Recursive setTimeout continues after unmount.

Excessive unknown types in API service (Medium)

• src/frontend/src/services/api.ts: Multiple methods return unknown or { items: unknown[] }, undermining TypeScript safety.

Duplicated catalogUrl with different base URLs (Medium, likely bug)

• RecCard.tsx:34 uses demo.redhat.com vs BrowsePage.tsx:103 uses catalog.demo.redhat.com — one is likely wrong.

cc @stencell