Update configuration and documentation

- Update .env.example with latest environment variables
- Update deployment and task documentation
- Update backend configuration settings

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

backend/app/config.py

@@ -120,11 +120,17 @@ class Settings(BaseSettings):
         ),
     )
     cors_allowed_origins: str | list[str] = Field(
-        default_factory=list,
+        default_factory=lambda: [
+            "http://localhost:5173",
+            "http://127.0.0.1:5173",
+            "https://localhost:5173",
+            "https://127.0.0.1:5173",
+        ],
         description=(
             "Comma-separated list of allowed CORS origins when the frontend is "
             "served from a different origin than the backend. "
-            "Leave empty to disable cross-origin requests in production."
+            "Defaults to common localhost development origins. "
+            "Override in production with the specific frontend domain."
         ),
     )