security: remove hardcoded credentials from scripts and docs

scripts/seed_admin.py

@@ -5,7 +5,7 @@ Usage: python scripts/seed_admin.py
 
 Creates:
   - Tenant: "Default Org" (slug: default)
-  - Admin user: admin@media-on.de / Admin123!
+  - Admin user: admin@media-on.de / (password from ADMIN_PASSWORD env var)
 
 If tenant or user already exists, skips creation.
 """
@@ -52,7 +52,7 @@ async def seed():
                 tenant_id=tenant.id,
                 email="admin@media-on.de",
                 name="Administrator",
-                password_hash=hash_password("Admin123!"),
+                password_hash=hash_password(os.environ.get("ADMIN_PASSWORD", "changeme")),
                 role="admin",
                 is_active=True,
                 preferences={},
@@ -72,7 +72,7 @@ async def seed():
         print("\nSeed complete!")
         print(f"  Login URL: https://crm.media-on.de/login")
         print(f"  Email:     admin@media-on.de")
-        print(f"  Password:   Admin123!")
+        print(f"  Password:   (from ADMIN_PASSWORD env var)")
 
     await close_engine()