feat(manager): add Nexus Instance Manager for demo orchestration

- Complete Flask-based control panel for multi-tenant POS instances
- Dashboard with global stats, system health, and recent demos
- Demo provisioning in 1 click with auto-expiration tracking
- Tenant management: activate/deactivate, reset data, delete
- Health monitoring: PostgreSQL, Redis, disk, memory, systemd services
- Migration orchestration UI for running schema updates across all tenants
- JWT authentication with manager_users table
- Dark theme SPA frontend with real-time search and actions
- systemd service file included

manager/config.py

@@ -0,0 +1,50 @@
+"""Nexus Instance Manager — Configuration."""
+import os
+
+# ─── Database ──────────────────────────────────────────────────────────────
+MASTER_DB_URL = os.environ.get("MASTER_DB_URL") or os.environ.get("DATABASE_URL")
+if not MASTER_DB_URL:
+    raise ValueError(
+        "MASTER_DB_URL environment variable is required. "
+        "Example: postgresql://user:pass@localhost/nexus_autoparts"
+    )
+
+TENANT_DB_URL_TEMPLATE = os.environ.get("TENANT_DB_URL_TEMPLATE")
+if not TENANT_DB_URL_TEMPLATE:
+    raise ValueError(
+        "TENANT_DB_URL_TEMPLATE environment variable is required. "
+        "Example: postgresql://user:pass@localhost/{db_name}"
+    )
+
+# ─── Security ──────────────────────────────────────────────────────────────
+MANAGER_JWT_SECRET = os.environ.get("MANAGER_JWT_SECRET")
+if not MANAGER_JWT_SECRET:
+    raise ValueError(
+        "MANAGER_JWT_SECRET environment variable is required. "
+        "Generate one with: python3 -c 'import secrets; print(secrets.token_hex(32))'"
+    )
+
+MANAGER_JWT_EXPIRES = int(os.environ.get("MANAGER_JWT_EXPIRES", "28800"))  # 8 hours
+
+# Internal API key for manager-to-POS operations
+INTERNAL_API_KEY = os.environ.get("INTERNAL_API_KEY", "")
+
+# ─── Demo Settings ─────────────────────────────────────────────────────────
+DEMO_DEFAULT_DAYS = int(os.environ.get("DEMO_DEFAULT_DAYS", "14"))
+DEMO_DEFAULT_PIN = os.environ.get("DEMO_DEFAULT_PIN", "0000")
+DEMO_SUBDOMAIN_PREFIX = os.environ.get("DEMO_SUBDOMAIN_PREFIX", "demo")
+
+# ─── Services Health Check ─────────────────────────────────────────────────
+POS_URL = os.environ.get("POS_URL", "http://127.0.0.1:5001/pos/health")
+DASHBOARD_URL = os.environ.get("DASHBOARD_URL", "http://127.0.0.1:5000/")
+QUART_URL = os.environ.get("QUART_URL", "http://127.0.0.1:5002/")
+REDIS_URL = os.environ.get("REDIS_URL", "redis://localhost:6379/0")
+
+# ─── Paths ─────────────────────────────────────────────────────────────────
+BASE_DIR = os.path.dirname(os.path.abspath(__file__))
+POS_DIR = os.environ.get("POS_DIR", "/home/Autopartes/pos")
+MIGRATIONS_DIR = os.path.join(POS_DIR, "migrations")
+
+# ─── App Identity ──────────────────────────────────────────────────────────
+APP_NAME = "Nexus Instance Manager"
+APP_VERSION = "1.0.0"