feat: database schema and connection

src/db/index.ts

@@ -0,0 +1,17 @@
+import Database from 'better-sqlite3';
+import { applySchema } from './schema';
+
+let _db: Database.Database | null = null;
+
+export function getDb(path: string = ':memory:'): Database.Database {
+  if (_db) return _db;
+  _db = new Database(path);
+  _db.pragma('journal_mode = WAL');
+  _db.pragma('foreign_keys = ON');
+  applySchema(_db);
+  return _db;
+}
+
+export function resetDb(): void {
+  _db = null;
+}

src/db/schema.ts

@@ -0,0 +1,28 @@
+import type { Database } from 'better-sqlite3';
+
+export function applySchema(db: Database): void {
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS sessions (
+      id           INTEGER PRIMARY KEY AUTOINCREMENT,
+      date         TEXT NOT NULL,
+      duration_min INTEGER NOT NULL,
+      notes        TEXT,
+      created_at   TEXT NOT NULL DEFAULT (datetime('now'))
+    );
+
+    CREATE TABLE IF NOT EXISTS schedule (
+      id            INTEGER PRIMARY KEY AUTOINCREMENT,
+      date          TEXT NOT NULL UNIQUE,
+      planned_min   INTEGER NOT NULL,
+      status        TEXT NOT NULL DEFAULT 'pending',
+      skip_reason   TEXT,
+      ai_rationale  TEXT,
+      created_at    TEXT NOT NULL DEFAULT (datetime('now'))
+    );
+
+    CREATE TABLE IF NOT EXISTS settings (
+      key   TEXT PRIMARY KEY,
+      value TEXT NOT NULL
+    );
+  `);
+}