feat(installer): J6412 USB installer + AR Electronics license activation server

installer/:
  - build_usb.py: dev tool — builds Flutter + AR-ECDIS, assembles USB pendrive
    image with serial.key, autorun.inf, and START_INSTALLER.bat
  - serial_generator.py: generates AR-XXXX-XXXX-XXXX serial numbers (48-bit
    entropy), logs to CSV for CRM integration
  - src/license.py: hardware fingerprint (Windows MachineGuid + primary MAC),
    serial validation, online activation POST, local cache with 30-day offline
    grace period
  - src/sysconfig.py: HKCU autostart registry entries, .lnk shortcuts (desktop
    + Start Menu via WScript.Shell), firewall rules (netsh), COM port detection
  - src/install.py: tkinter installer GUI — 9 sequential steps with per-step
    progress indicators, threaded execution, error dialogs, and silent mode

license_server/ (FastAPI service — deploy to arelectronics.com VPS):
  - POST /api/v1/activate: first activation accepted; same-HW re-activation
    refreshes heartbeat; different-HW rejected with 409
  - GET  /api/v1/validate/{serial}: heartbeat endpoint to refresh offline cache
  - Admin endpoints (X-Admin-Key): issue, list, revoke licenses
  - SQLAlchemy models: License (serial registry) + Activation (per-machine rows)
  - SQLite default, PostgreSQL-ready via DATABASE_URL env var

AR_electronics — AR-Autopilot Project

license_server/database.py

@@ -0,0 +1,33 @@
+# =============================================================================
+#  license_server/database.py — SQLAlchemy engine + session factory
+# =============================================================================
+
+import os
+from sqlalchemy import create_engine
+from sqlalchemy.orm import DeclarativeBase, sessionmaker
+
+# Default: SQLite in same directory.  Set DATABASE_URL env var for PostgreSQL.
+DATABASE_URL = os.getenv(
+    "DATABASE_URL",
+    "sqlite:///./ar_licenses.db",
+)
+
+# connect_args only needed for SQLite (allows multi-threaded use by FastAPI)
+_connect_args = {"check_same_thread": False} if DATABASE_URL.startswith("sqlite") else {}
+
+engine = create_engine(DATABASE_URL, connect_args=_connect_args)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+def get_db():
+    """FastAPI dependency that yields a database session."""
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()