feat: initialize Django backend project structure

Sets up Django 4.2 project skeleton with split settings (base/development),
JWT auth via simplejwt, DRF, CORS, PostgreSQL, Redis cache config, and
.gitignore. Apps (accounts, organizations, jobs, resumes, applications)
to be created in subsequent tasks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

offer_backend/.gitignore

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+.env
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+.Python
+*.egg-info/
+dist/
+build/
+media/
+staticfiles/
+db.sqlite3

offer_backend/config/asgi.py

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+"""
+ASGI config for config project.
+
+It exposes the ASGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/4.2/howto/deployment/asgi/
+"""
+
+import os
+
+from django.core.asgi import get_asgi_application
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'config.settings')
+
+application = get_asgi_application()

offer_backend/config/settings/base.py

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+from pathlib import Path
+from decouple import config
+
+BASE_DIR = Path(__file__).resolve().parent.parent.parent
+
+SECRET_KEY = config('SECRET_KEY')
+
+INSTALLED_APPS = [
+    'django.contrib.admin',
+    'django.contrib.auth',
+    'django.contrib.contenttypes',
+    'django.contrib.sessions',
+    'django.contrib.messages',
+    'django.contrib.staticfiles',
+    # Third party
+    'rest_framework',
+    'rest_framework_simplejwt',
+    'corsheaders',
+    'django_filters',
+    # Local
+    'apps.accounts',
+    'apps.organizations',
+    'apps.jobs',
+    'apps.resumes',
+    'apps.applications',
+]
+
+MIDDLEWARE = [
+    'django.middleware.security.SecurityMiddleware',
+    'corsheaders.middleware.CorsMiddleware',
+    'django.contrib.sessions.middleware.SessionMiddleware',
+    'django.middleware.common.CommonMiddleware',
+    'django.middleware.csrf.CsrfViewMiddleware',
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.messages.middleware.MessageMiddleware',
+    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+]
+
+ROOT_URLCONF = 'config.urls'
+
+TEMPLATES = [
+    {
+        'BACKEND': 'django.template.backends.django.DjangoTemplates',
+        'DIRS': [],
+        'APP_DIRS': True,
+        'OPTIONS': {
+            'context_processors': [
+                'django.template.context_processors.debug',
+                'django.template.context_processors.request',
+                'django.contrib.auth.context_processors.auth',
+                'django.contrib.messages.context_processors.messages',
+            ],
+        },
+    },
+]
+
+AUTH_USER_MODEL = 'accounts.User'
+
+REST_FRAMEWORK = {
+    'DEFAULT_AUTHENTICATION_CLASSES': (
+        'rest_framework_simplejwt.authentication.JWTAuthentication',
+    ),
+    'DEFAULT_PERMISSION_CLASSES': (
+        'rest_framework.permissions.IsAuthenticated',
+    ),
+    'DEFAULT_FILTER_BACKENDS': [
+        'django_filters.rest_framework.DjangoFilterBackend',
+        'rest_framework.filters.SearchFilter',
+        'rest_framework.filters.OrderingFilter',
+    ],
+    'DEFAULT_PAGINATION_CLASS': 'rest_framework.pagination.PageNumberPagination',
+    'PAGE_SIZE': 20,
+}
+
+from datetime import timedelta
+SIMPLE_JWT = {
+    'ACCESS_TOKEN_LIFETIME': timedelta(hours=2),
+    'REFRESH_TOKEN_LIFETIME': timedelta(days=7),
+}
+
+STATIC_URL = '/static/'
+MEDIA_URL = '/media/'
+MEDIA_ROOT = BASE_DIR / 'media'
+
+DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'
+LANGUAGE_CODE = 'zh-hans'
+TIME_ZONE = 'Asia/Shanghai'
+USE_I18N = True
+USE_TZ = True

offer_backend/config/settings/development.py

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+from .base import *
+
+DEBUG = True
+ALLOWED_HOSTS = ['*']
+
+DATABASES = {
+    'default': {
+        'ENGINE': 'django.db.backends.postgresql',
+        'NAME': config('DB_NAME', default='offer_db'),
+        'USER': config('DB_USER', default='postgres'),
+        'PASSWORD': config('DB_PASSWORD', default='postgres'),
+        'HOST': config('DB_HOST', default='localhost'),
+        'PORT': config('DB_PORT', default='5432'),
+    }
+}
+
+CACHES = {
+    'default': {
+        'BACKEND': 'django_redis.cache.RedisCache',
+        'LOCATION': config('REDIS_URL', default='redis://127.0.0.1:6379/1'),
+    }
+}
+
+CORS_ALLOW_ALL_ORIGINS = True
+
+EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'

offer_backend/config/urls.py

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+from django.contrib import admin
+from django.urls import path, include
+from django.conf import settings
+from django.conf.urls.static import static
+
+urlpatterns = [
+    path('admin/', admin.site.urls),
+    path('api/auth/', include('apps.accounts.urls')),
+    path('api/organizations/', include('apps.organizations.urls')),
+    path('api/jobs/', include('apps.jobs.urls')),
+    path('api/resumes/', include('apps.resumes.urls')),
+    path('api/applications/', include('apps.applications.urls')),
+] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

offer_backend/config/wsgi.py

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+"""
+WSGI config for config project.
+
+It exposes the WSGI callable as a module-level variable named ``application``.
+
+For more information on this file, see
+https://docs.djangoproject.com/en/4.2/howto/deployment/wsgi/
+"""
+
+import os
+
+from django.core.wsgi import get_wsgi_application
+
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'config.settings')
+
+application = get_wsgi_application()

offer_backend/manage.py

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+#!/usr/bin/env python
+"""Django's command-line utility for administrative tasks."""
+import os
+import sys
+
+
+def main():
+    """Run administrative tasks."""
+    os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'config.settings')
+    try:
+        from django.core.management import execute_from_command_line
+    except ImportError as exc:
+        raise ImportError(
+            "Couldn't import Django. Are you sure it's installed and "
+            "available on your PYTHONPATH environment variable? Did you "
+            "forget to activate a virtual environment?"
+        ) from exc
+    execute_from_command_line(sys.argv)
+
+
+if __name__ == '__main__':
+    main()

offer_backend/requirements.txt

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+Django==4.2.20
+djangorestframework==3.16.0
+djangorestframework-simplejwt==5.3.1
+django-cors-headers==4.3.1
+django-filter==23.5
+psycopg2-binary==2.9.9
+redis==5.0.1
+django-redis==5.4.0
+Pillow==10.3.0
+python-decouple==3.8