feat: US-002 — SQLite + Drizzle ORM schema and migrations

- Install better-sqlite3 + drizzle-orm as runtime deps; drizzle-kit + @types/better-sqlite3 as devDeps
- Define 5 tables in src/main/db/schema.ts: clients, projects, tasks, checkpoints, notes
- All IDs are TEXT (UUID); types inferred via InferSelectModel/InferInsertModel
- initDb() in src/main/db/index.ts opens adiuva.db at app.getPath('userData'), runs CREATE TABLE IF NOT EXISTS (non-destructive push), enables WAL mode
- Call initDb() in main process app ready handler
- Externalize better-sqlite3 in vite.main.config.mts; add AutoUnpackNativesPlugin to forge.config.ts
- Add drizzle.config.ts for drizzle-kit CLI support

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

src/main/db/index.ts

@@ -0,0 +1,83 @@
+import Database from 'better-sqlite3';
+import { drizzle } from 'drizzle-orm/better-sqlite3';
+import { app } from 'electron';
+import path from 'node:path';
+import * as schema from './schema';
+
+// SQL to create all tables if they don't exist (non-destructive push strategy)
+const MIGRATION_SQL = `
+  CREATE TABLE IF NOT EXISTS clients (
+    id TEXT PRIMARY KEY,
+    parent_id TEXT,
+    name TEXT NOT NULL,
+    industry TEXT,
+    created_at INTEGER NOT NULL
+  );
+
+  CREATE TABLE IF NOT EXISTS projects (
+    id TEXT PRIMARY KEY,
+    client_id TEXT,
+    name TEXT NOT NULL,
+    status TEXT NOT NULL DEFAULT 'active',
+    ai_summary TEXT,
+    created_at INTEGER NOT NULL
+  );
+
+  CREATE TABLE IF NOT EXISTS tasks (
+    id TEXT PRIMARY KEY,
+    project_id TEXT,
+    title TEXT NOT NULL,
+    description TEXT,
+    status TEXT NOT NULL DEFAULT 'todo',
+    priority TEXT NOT NULL DEFAULT 'medium',
+    assignee TEXT,
+    due_date INTEGER,
+    created_at INTEGER NOT NULL
+  );
+
+  CREATE TABLE IF NOT EXISTS checkpoints (
+    id TEXT PRIMARY KEY,
+    project_id TEXT NOT NULL,
+    title TEXT NOT NULL,
+    date INTEGER NOT NULL,
+    is_ai_suggested INTEGER NOT NULL DEFAULT 0,
+    is_approved INTEGER NOT NULL DEFAULT 0,
+    created_at INTEGER NOT NULL
+  );
+
+  CREATE TABLE IF NOT EXISTS notes (
+    id TEXT PRIMARY KEY,
+    project_id TEXT,
+    title TEXT NOT NULL,
+    content TEXT NOT NULL DEFAULT '',
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL
+  );
+`;
+
+type DbInstance = ReturnType<typeof drizzle<typeof schema>>;
+
+let dbInstance: DbInstance | null = null;
+
+export function initDb(): DbInstance {
+  const userDataPath = app.getPath('userData');
+  const dbPath = path.join(userDataPath, 'adiuva.db');
+
+  const sqlite = new Database(dbPath);
+
+  // Enable WAL mode for better concurrent read performance
+  sqlite.pragma('journal_mode = WAL');
+
+  // Run non-destructive migrations on every start
+  sqlite.exec(MIGRATION_SQL);
+
+  dbInstance = drizzle(sqlite, { schema });
+  return dbInstance;
+}
+
+export function getDb(): DbInstance {
+  if (!dbInstance) {
+    throw new Error('Database not initialized. Call initDb() first.');
+  }
+  return dbInstance;
+}