feat: add Django backend foundation and Docker runtime

Add a Django admin-backed management layer for pobsync configs, runs,
snapshots, and schedules. Keep the existing CLI engine as the execution
source of truth, add import/run management commands, and provide SQLite
default plus optional MariaDB Docker Compose support.

src/pobsync_server/__init__.py

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+

src/pobsync_server/asgi.py

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+from __future__ import annotations
+
+import os
+
+from django.core.asgi import get_asgi_application
+
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "pobsync_server.settings")
+
+application = get_asgi_application()

src/pobsync_server/settings.py

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+from __future__ import annotations
+
+import os
+from pathlib import Path
+
+
+BASE_DIR = Path(__file__).resolve().parents[2]
+
+SECRET_KEY = os.getenv("POBSYNC_DJANGO_SECRET_KEY", "dev-only-change-me")
+DEBUG = os.getenv("POBSYNC_DJANGO_DEBUG", "0").lower() in {"1", "true", "yes", "on"}
+
+_allowed_hosts = os.getenv("POBSYNC_DJANGO_ALLOWED_HOSTS", "localhost,127.0.0.1")
+ALLOWED_HOSTS = [host.strip() for host in _allowed_hosts.split(",") if host.strip()]
+
+INSTALLED_APPS = [
+    "django.contrib.admin",
+    "django.contrib.auth",
+    "django.contrib.contenttypes",
+    "django.contrib.sessions",
+    "django.contrib.messages",
+    "django.contrib.staticfiles",
+    "pobsync_backend.apps.PobsyncBackendConfig",
+]
+
+MIDDLEWARE = [
+    "django.middleware.security.SecurityMiddleware",
+    "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 = "pobsync_server.urls"
+
+TEMPLATES = [
+    {
+        "BACKEND": "django.template.backends.django.DjangoTemplates",
+        "DIRS": [],
+        "APP_DIRS": True,
+        "OPTIONS": {
+            "context_processors": [
+                "django.template.context_processors.request",
+                "django.contrib.auth.context_processors.auth",
+                "django.contrib.messages.context_processors.messages",
+            ],
+        },
+    },
+]
+
+WSGI_APPLICATION = "pobsync_server.wsgi.application"
+
+
+def _database_config() -> dict[str, object]:
+    engine = os.getenv("POBSYNC_DB_ENGINE", "sqlite").strip().lower()
+    if engine in {"mariadb", "mysql"}:
+        return {
+            "ENGINE": "django.db.backends.mysql",
+            "NAME": os.getenv("POBSYNC_DB_NAME", "pobsync"),
+            "USER": os.getenv("POBSYNC_DB_USER", "pobsync"),
+            "PASSWORD": os.getenv("POBSYNC_DB_PASSWORD", "pobsync"),
+            "HOST": os.getenv("POBSYNC_DB_HOST", "db"),
+            "PORT": os.getenv("POBSYNC_DB_PORT", "3306"),
+            "OPTIONS": {
+                "charset": "utf8mb4",
+            },
+        }
+
+    sqlite_path = os.getenv("POBSYNC_SQLITE_PATH", str(BASE_DIR / "var" / "pobsync.sqlite3"))
+    return {
+        "ENGINE": "django.db.backends.sqlite3",
+        "NAME": sqlite_path,
+    }
+
+
+DATABASES = {
+    "default": _database_config(),
+}
+
+LANGUAGE_CODE = "en-us"
+TIME_ZONE = os.getenv("POBSYNC_TIME_ZONE", "UTC")
+USE_I18N = True
+USE_TZ = True
+
+STATIC_URL = "static/"
+STATIC_ROOT = os.getenv("POBSYNC_STATIC_ROOT", str(BASE_DIR / "var" / "static"))
+
+DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
+
+POBSYNC_HOME = os.getenv("POBSYNC_HOME", "/opt/pobsync")

src/pobsync_server/urls.py

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+from __future__ import annotations
+
+from django.contrib import admin
+from django.urls import path
+
+
+urlpatterns = [
+    path("admin/", admin.site.urls),
+]

src/pobsync_server/wsgi.py

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+from __future__ import annotations
+
+import os
+
+from django.core.wsgi import get_wsgi_application
+
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "pobsync_server.settings")
+
+application = get_wsgi_application()