feat(10-01): wire pros/cons through client hooks, form, and card indicator

- CandidateResponse: add pros/cons string|null fields
- CandidateForm: add pros/cons to FormData, INITIAL_FORM, pre-fill, payload
- CandidateForm: add Pros/Cons textarea inputs (after Notes, before Product Link)
- CandidateCard: add pros/cons props, render purple +/- Notes badge when present
- Thread detail route: pass pros/cons props to CandidateCard

src/client/routes/threads/$threadId.tsx

@@ -153,6 +153,8 @@ function ThreadDetailPage() {
 									status: newStatus,
 								})
 							}
+							pros={candidate.pros}
+							cons={candidate.cons}
 						/>
 					))}
 				</div>