feat: auth middleware, brain data layer, Valkey queue (P1-002, P1-003, P1-004)

Auth middleware (P1-002):
- DatabaseModule provides Db instance with graceful shutdown
- AuthModule mounts BetterAuth at /api/auth/* via toNodeHandler
- AuthGuard validates sessions via BetterAuth API
- CurrentUser decorator extracts user from request

Brain data layer (P1-003):
- CRUD repositories for projects, missions, tasks, conversations
- createBrain(db) factory returns all repositories
- Re-exports drizzle-orm query helpers from @mosaic/db to avoid
  duplicate package resolution

Queue (P1-004):
- ioredis-based Valkey client with createQueue/createQueueClient
- Enqueue/dequeue, pub/sub, queue length operations

Closes #11, Closes #12, Closes #13

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/brain/src/projects.ts

@@ -0,0 +1,38 @@
+import { eq, type Db, projects } from '@mosaic/db';
+
+export type Project = typeof projects.$inferSelect;
+export type NewProject = typeof projects.$inferInsert;
+
+export function createProjectsRepo(db: Db) {
+  return {
+    async findAll(): Promise<Project[]> {
+      return db.select().from(projects);
+    },
+
+    async findById(id: string): Promise<Project | undefined> {
+      const rows = await db.select().from(projects).where(eq(projects.id, id));
+      return rows[0];
+    },
+
+    async create(data: NewProject): Promise<Project> {
+      const rows = await db.insert(projects).values(data).returning();
+      return rows[0]!;
+    },
+
+    async update(id: string, data: Partial<NewProject>): Promise<Project | undefined> {
+      const rows = await db
+        .update(projects)
+        .set({ ...data, updatedAt: new Date() })
+        .where(eq(projects.id, id))
+        .returning();
+      return rows[0];
+    },
+
+    async remove(id: string): Promise<boolean> {
+      const rows = await db.delete(projects).where(eq(projects.id, id)).returning();
+      return rows.length > 0;
+    },
+  };
+}
+
+export type ProjectsRepo = ReturnType<typeof createProjectsRepo>;