feat(04-01): update thread service, routes, and hooks for categoryId

- createThread now inserts categoryId from data
- getAllThreads joins categories table, returns categoryName/categoryEmoji
- updateThread accepts optional categoryId
- ThreadListItem interface includes category fields
- useCreateThread hook sends categoryId
- Fix test files to pass categoryId when creating threads

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

src/server/services/thread.service.ts

@@ -8,7 +8,7 @@ type Db = typeof prodDb;
 export function createThread(db: Db = prodDb, data: CreateThread) {
   return db
     .insert(threads)
-    .values({ name: data.name })
+    .values({ name: data.name, categoryId: data.categoryId })
     .returning()
     .get();
 }
@@ -20,6 +20,9 @@ export function getAllThreads(db: Db = prodDb, includeResolved = false) {
       name: threads.name,
       status: threads.status,
       resolvedCandidateId: threads.resolvedCandidateId,
+      categoryId: threads.categoryId,
+      categoryName: categories.name,
+      categoryEmoji: categories.emoji,
       createdAt: threads.createdAt,
       updatedAt: threads.updatedAt,
       candidateCount: sql<number>`(
@@ -36,6 +39,7 @@ export function getAllThreads(db: Db = prodDb, includeResolved = false) {
       )`.as("max_price_cents"),
     })
     .from(threads)
+    .innerJoin(categories, eq(threads.categoryId, categories.id))
     .orderBy(desc(threads.createdAt));
 
   if (!includeResolved) {
@@ -73,7 +77,7 @@ export function getThreadWithCandidates(db: Db = prodDb, threadId: number) {
   return { ...thread, candidates: candidateList };
 }
 
-export function updateThread(db: Db = prodDb, threadId: number, data: Partial<{ name: string }>) {
+export function updateThread(db: Db = prodDb, threadId: number, data: Partial<{ name: string; categoryId: number }>) {
   const existing = db.select({ id: threads.id }).from(threads)
     .where(eq(threads.id, threadId)).get();
   if (!existing) return null;