feat(02-02): add thread detail page with candidate CRUD and resolution flow

- Create CandidateCard with edit, delete, and pick winner actions
- Create CandidateForm with same fields as ItemForm for candidate add/edit
- Build thread detail page with candidate grid and resolution banner
- Update root layout with candidate panel, delete dialog, and resolve dialog
- Hide FAB on thread detail pages, keep it for gear tab
- Resolution navigates back to planning tab after success

src/client/components/CandidateCard.tsx

@@ -0,0 +1,91 @@
+import { formatWeight, formatPrice } from "../lib/formatters";
+import { useUIStore } from "../stores/uiStore";
+
+interface CandidateCardProps {
+  id: number;
+  name: string;
+  weightGrams: number | null;
+  priceCents: number | null;
+  categoryName: string;
+  categoryEmoji: string;
+  imageFilename: string | null;
+  threadId: number;
+  isActive: boolean;
+}
+
+export function CandidateCard({
+  id,
+  name,
+  weightGrams,
+  priceCents,
+  categoryName,
+  categoryEmoji,
+  imageFilename,
+  threadId,
+  isActive,
+}: CandidateCardProps) {
+  const openCandidateEditPanel = useUIStore((s) => s.openCandidateEditPanel);
+  const openConfirmDeleteCandidate = useUIStore(
+    (s) => s.openConfirmDeleteCandidate,
+  );
+  const openResolveDialog = useUIStore((s) => s.openResolveDialog);
+
+  return (
+    <div className="bg-white rounded-xl border border-gray-100 hover:border-gray-200 hover:shadow-sm transition-all overflow-hidden">
+      {imageFilename && (
+        <div className="aspect-[4/3] bg-gray-50">
+          <img
+            src={`/uploads/${imageFilename}`}
+            alt={name}
+            className="w-full h-full object-cover"
+          />
+        </div>
+      )}
+      <div className="p-4">
+        <h3 className="text-sm font-semibold text-gray-900 mb-2 truncate">
+          {name}
+        </h3>
+        <div className="flex flex-wrap gap-1.5 mb-3">
+          {weightGrams != null && (
+            <span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-blue-50 text-blue-700">
+              {formatWeight(weightGrams)}
+            </span>
+          )}
+          {priceCents != null && (
+            <span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-green-50 text-green-700">
+              {formatPrice(priceCents)}
+            </span>
+          )}
+          <span className="inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-gray-50 text-gray-600">
+            {categoryEmoji} {categoryName}
+          </span>
+        </div>
+        <div className="flex gap-2">
+          <button
+            type="button"
+            onClick={() => openCandidateEditPanel(id)}
+            className="text-xs text-gray-500 hover:text-blue-600 transition-colors"
+          >
+            Edit
+          </button>
+          <button
+            type="button"
+            onClick={() => openConfirmDeleteCandidate(id)}
+            className="text-xs text-gray-500 hover:text-red-600 transition-colors"
+          >
+            Delete
+          </button>
+          {isActive && (
+            <button
+              type="button"
+              onClick={() => openResolveDialog(threadId, id)}
+              className="ml-auto text-xs font-medium text-amber-600 hover:text-amber-700 transition-colors"
+            >
+              Pick Winner
+            </button>
+          )}
+        </div>
+      </div>
+    </div>
+  );
+}