Backend refactoring updates

- Update Docker compose debug configuration
- Update backend documentation
- Update tasks documentation
- Update backend config module

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Docs/Backend-Development.md

@@ -506,6 +506,22 @@ class Settings(BaseSettings):
     model_config = {"env_prefix": "BANGUI_", "env_file": ".env"}
 ```
 
+### Session Cookie Security
+
+The `session_cookie_secure` configuration controls the `Secure` flag on the session cookie. This flag prevents browsers from sending the session cookie over unencrypted HTTP.
+
+**Default:** `true` — Production deployments are secure by default. Cookies are only sent over HTTPS.
+
+**Local Development:** Set `BANGUI_SESSION_COOKIE_SECURE=false` in your compose file or `.env` to allow cookies over HTTP (required for `localhost:8000`).
+
+```yaml
+# Docker/compose.debug.yml
+environment:
+  BANGUI_SESSION_COOKIE_SECURE: "false"  # Allow HTTP during local development
+```
+
+**Important:** If `Secure=true` is set, browsers will reject the session cookie when the backend is served over HTTP. Ensure your nginx/reverse proxy terminates TLS and passes `X-Forwarded-Proto: https` so FastAPI knows the connection is secure.
+
 ---
 
 ## 13. Git & Workflow