feat: major project restructure - move Django to backend dir and fix critical imports

- Restructure project: moved Django backend to backend/ directory
- Add frontend/ directory for future Next.js application
- Add shared/ directory for common resources
- Fix critical Django import errors:
  - Add missing sys.path modification for apps directory
  - Fix undefined CATEGORY_CHOICES imports in rides module
  - Fix media migration undefined references
  - Remove unused imports and f-strings without placeholders
- Install missing django-environ dependency
- Django server now runs without ModuleNotFoundError
- Update .gitignore and README for new structure
- Add pnpm workspace configuration for monorepo setup

config/settings/database.py

@@ -1,28 +0,0 @@
-"""
-Database configuration for thrillwiki project.
-"""
-
-import environ
-
-env = environ.Env()
-
-# Database configuration
-db_config = env.db("DATABASE_URL")
-
-
-# Force PostGIS backend for spatial data support
-db_config["ENGINE"] = "django.contrib.gis.db.backends.postgis"
-
-DATABASES = {
-    "default": db_config,
-}
-
-# GeoDjango Settings - Environment specific
-GDAL_LIBRARY_PATH = env("GDAL_LIBRARY_PATH", default=None)
-GEOS_LIBRARY_PATH = env("GEOS_LIBRARY_PATH", default=None)
-
-# Cache settings
-CACHES = {"default": env.cache("CACHE_URL", default="locmemcache://")}
-
-CACHE_MIDDLEWARE_SECONDS = env.int("CACHE_MIDDLEWARE_SECONDS", default=300)  # 5 minutes
-CACHE_MIDDLEWARE_KEY_PREFIX = env("CACHE_MIDDLEWARE_KEY_PREFIX", default="thrillwiki")