Typecheck tests against current types

tsx runs tests without type checking and tsconfig.json covers only src,
so 71 type errors had accumulated unnoticed. tsconfig.tests.json now
checks every test and helper, and npm run typecheck includes it.

Fixtures gain the fields the DTOs have grown since they were written
(manualQuantity, circuit apparent power/cos phi, downstream board loads,
section totals, building, cover and board info fields). Repository
lookups that return "row ?? null" now declare the null in their type,
which their callers already handle.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/db/repositories/circuit-list.repository.ts

@@ -10,7 +10,7 @@ export class CircuitListRepository {
     return db.select().from(circuitLists).where(eq(circuitLists.projectId, projectId));
   }
 
-  async findById(projectId: string, circuitListId: string) {
+  async findById(projectId: string, circuitListId: string): Promise<typeof circuitLists.$inferSelect | null> {
     const db = this.database;
     const [row] = await db
       .select()

src/db/repositories/circuit-section.repository.ts

@@ -15,7 +15,7 @@ export function createDefaultCircuitSectionValues(circuitListId: string) {
 export class CircuitSectionRepository {
   constructor(private readonly database: AppDatabase) {}
 
-  async findById(sectionId: string) {
+  async findById(sectionId: string): Promise<typeof circuitSections.$inferSelect | null> {
     const db = this.database;
     const [row] = await db.select().from(circuitSections).where(eq(circuitSections.id, sectionId)).limit(1);
     return row ?? null;

src/db/repositories/global-device.repository.ts

@@ -53,7 +53,7 @@ export class GlobalDeviceRepository {
       .where(eq(globalDevices.id, globalDeviceId));
   }
 
-  async findById(globalDeviceId: string) {
+  async findById(globalDeviceId: string): Promise<typeof globalDevices.$inferSelect | null> {
     const db = this.database;
     const [row] = await db.select().from(globalDevices).where(eq(globalDevices.id, globalDeviceId)).limit(1);
     return row ?? null;

src/db/repositories/project.repository.ts

@@ -41,7 +41,7 @@ export class ProjectRepository {
     return project;
   }
 
-  async findById(projectId: string) {
+  async findById(projectId: string): Promise<typeof projects.$inferSelect | null> {
     const db = this.database;
     const [row] = await db.select().from(projects).where(eq(projects.id, projectId)).limit(1);
     return row ?? null;

src/db/repositories/user.repository.ts

@@ -32,13 +32,13 @@ export class UserRepository implements UserStore {
     return rows.length;
   }
 
-  async findById(userId: string) {
+  async findById(userId: string): Promise<typeof users.$inferSelect | null> {
     const db = this.database;
     const [row] = await db.select().from(users).where(eq(users.id, userId)).limit(1);
     return row ?? null;
   }
 
-  async findByUsername(username: string) {
+  async findByUsername(username: string): Promise<typeof users.$inferSelect | null> {
     const db = this.database;
     const [row] = await db
       .select()