feat: initialize database and authentication routes in backend

backend/src/db/migrations.ts

@@ -0,0 +1,48 @@
+import type Database from 'better-sqlite3'
+
+export function runMigrations(db: Database.Database): void {
+  db.exec(`
+    CREATE TABLE IF NOT EXISTS users (
+      id             INTEGER PRIMARY KEY AUTOINCREMENT,
+      email          TEXT UNIQUE NOT NULL,
+      password_hash  TEXT NOT NULL,
+      display_name   TEXT NOT NULL,
+      email_verified INTEGER DEFAULT 0,
+      verify_token   TEXT,
+      verify_expires INTEGER,
+      reset_token    TEXT,
+      reset_expires  INTEGER,
+      created_at     INTEGER DEFAULT (unixepoch()),
+      updated_at     INTEGER DEFAULT (unixepoch())
+    );
+
+    CREATE TABLE IF NOT EXISTS saved_exams (
+      id          INTEGER PRIMARY KEY AUTOINCREMENT,
+      user_id     INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      title       TEXT NOT NULL,
+      subtitle    TEXT,
+      exam_json   TEXT NOT NULL,
+      created_at  INTEGER DEFAULT (unixepoch()),
+      updated_at  INTEGER DEFAULT (unixepoch())
+    );
+
+    CREATE TABLE IF NOT EXISTS exam_results (
+      id            INTEGER PRIMARY KEY AUTOINCREMENT,
+      user_id       INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      exam_id       INTEGER REFERENCES saved_exams(id) ON DELETE SET NULL,
+      title         TEXT NOT NULL,
+      score_points  REAL NOT NULL,
+      total_points  REAL NOT NULL,
+      correct_count INTEGER NOT NULL,
+      graded_count  INTEGER NOT NULL,
+      passing_score REAL DEFAULT 60,
+      elapsed_ms    INTEGER NOT NULL,
+      state_json    TEXT NOT NULL,
+      exam_json     TEXT NOT NULL,
+      completed_at  INTEGER DEFAULT (unixepoch())
+    );
+
+    CREATE INDEX IF NOT EXISTS idx_saved_exams_user ON saved_exams(user_id);
+    CREATE INDEX IF NOT EXISTS idx_exam_results_user ON exam_results(user_id);
+  `)
+}