feat(lessons): implement comprehensive lesson configurator, session runner and AI debrief (Beta)

app/database.py

@@ -385,6 +385,40 @@ def _migrate(conn: sqlite3.Connection):
     conn.execute("CREATE INDEX IF NOT EXISTS idx_bg_tasks_user_status ON background_tasks(user_id, status);")
     conn.execute("CREATE INDEX IF NOT EXISTS idx_bg_tasks_status ON background_tasks(status);")
 
+    # Ensure lesson_presets and lesson_sessions tables exist (Lesson Configurator & Runner)
+    conn.execute("""
+    CREATE TABLE IF NOT EXISTS lesson_presets (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        user_id INTEGER NOT NULL,
+        name TEXT NOT NULL,
+        icon TEXT DEFAULT '🚀',
+        description TEXT DEFAULT '',
+        estimated_min INTEGER DEFAULT 15,
+        config_json TEXT NOT NULL,
+        is_default INTEGER DEFAULT 0,
+        created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+    );
+    """)
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_lesson_presets_user ON lesson_presets(user_id);")
+
+    conn.execute("""
+    CREATE TABLE IF NOT EXISTS lesson_sessions (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        user_id INTEGER NOT NULL,
+        preset_name TEXT NOT NULL,
+        duration_seconds INTEGER DEFAULT 0,
+        total_score INTEGER DEFAULT 0,
+        grade TEXT DEFAULT 'A',
+        steps_summary_json TEXT NOT NULL,
+        errors_json TEXT NOT NULL,
+        ai_report_json TEXT NOT NULL,
+        completed_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+        FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
+    );
+    """)
+    conn.execute("CREATE INDEX IF NOT EXISTS idx_lesson_sess_user_date ON lesson_sessions(user_id, completed_at DESC);")
+
     # Repair legacy cards with placeholder blanks or mismatched context
     repair_mismatched_cefr_contexts(conn)