Add local-first SPA architecture and containerized production deploy.

Move data access to use-cases and IndexedDB repositories with optional
remote fallback, changelog/sync ports, and encrypted local backup.
Add production Docker Compose (nginx frontend + optional backend) and
Apache host proxy configuration for deployment.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/config/settings.py

@@ -1,10 +1,16 @@
+import os
 from pathlib import Path
 
 BASE_DIR = Path(__file__).resolve().parent.parent
 
-SECRET_KEY = 'django-insecure-social-graph-dev-key-change-in-production'
-DEBUG = True
-ALLOWED_HOSTS = ['*']
+SECRET_KEY = os.environ.get(
+    'SECRET_KEY',
+    'django-insecure-social-graph-dev-key-change-in-production',
+)
+DEBUG = os.environ.get('DEBUG', 'True').lower() in ('1', 'true', 'yes')
+ALLOWED_HOSTS = [
+    h.strip() for h in os.environ.get('ALLOWED_HOSTS', '*').split(',') if h.strip()
+]
 
 INSTALLED_APPS = [
     'django.contrib.contenttypes',
@@ -25,7 +31,7 @@ ROOT_URLCONF = 'config.urls'
 DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': BASE_DIR / 'db.sqlite3',
+        'NAME': os.environ.get('DATABASE_PATH', str(BASE_DIR / 'db.sqlite3')),
     }
 }