Add database package with Drizzle schema

Postgres schema via Drizzle ORM for agents, goals, issues, projects,
and activity log tables. Includes migration runner, seed script,
and Drizzle config.

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

packages/db/src/schema/goals.ts

@@ -0,0 +1,13 @@
+import { type AnyPgColumn, pgTable, uuid, text, timestamp } from "drizzle-orm/pg-core";
+import { agents } from "./agents.js";
+
+export const goals = pgTable("goals", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  title: text("title").notNull(),
+  description: text("description"),
+  level: text("level").notNull().default("task"),
+  parentId: uuid("parent_id").references((): AnyPgColumn => goals.id),
+  ownerId: uuid("owner_id").references(() => agents.id),
+  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp("updated_at", { withTimezone: true }).notNull().defaultNow(),
+});