fix: prevent re-creation of deleted default client and project

Implements persistent flag tracking to ensure default client and project
are only created on fresh installations and never recreated after user
deletion during updates or restarts.

- Added initial_data_seeded flag to InstallationConfig
- Updated all 3 database initialization scripts to check flag
- Added 3 unit tests (all passing)
- Created comprehensive documentation

Fixes issue where defaults were recreated after deletion during updates.

docker/init-database.py

@@ -185,22 +185,35 @@ def initialize_database(engine):
             else:
                 print("Default settings already exist")
             
-            # Create default project if it doesn't exist
-            print("Checking for default project...")
-            if not Project.query.first():
-                print("Creating default project...")
-                project = Project(
-                    name='General',
-                    client='Default Client',
-                    description='Default project for general tasks',
-                    billable=True,
-                    status='active'
-                )
-                db.session.add(project)
-                db.session.commit()
-                print("Created default project")
+            # Import installation config to check if initial data has been seeded
+            from app.utils.installation import get_installation_config
+            installation_config = get_installation_config()
+            
+            # Only create default project/client on fresh installations
+            # Check if initial data has already been seeded
+            if not installation_config.is_initial_data_seeded():
+                print("Checking for default project...")
+                if not Project.query.first():
+                    print("Creating default project and client (fresh installation)...")
+                    project = Project(
+                        name='General',
+                        client='Default Client',
+                        description='Default project for general tasks',
+                        billable=True,
+                        status='active'
+                    )
+                    db.session.add(project)
+                    db.session.commit()
+                    print("Created default project and client")
+                    
+                    # Mark that initial data has been seeded
+                    installation_config.mark_initial_data_seeded()
+                    print("Marked initial data as seeded")
+                else:
+                    print("Projects already exist, marking initial data as seeded")
+                    installation_config.mark_initial_data_seeded()
             else:
-                print("Default project already exists")
+                print("Initial data already seeded previously, skipping default project/client creation")
             
             print("Database initialized successfully")
             return True