feat(auth): consolidate and secure V3 authentication flow

- Re-apply safe guest auth and passcode-to-JWT endpoint
- Consolidate AccountContext with token_payload and role flags
- Restore documentation for new guest flows and public read whitelists
- Fix 403 error in get_obj_li by allowing optional account context

app/routers/api_crud_v3.py

@@ -160,7 +160,7 @@ async def get_obj_li(
         view: str = Query('default'),
         order_by_li: Optional[str] = None,
         jp: Optional[Union[str, None]] = None,
-        account: AccountContext = Depends(get_account_context),
+        account: AccountContext = Depends(get_account_context_optional),
         pagination: PaginationParams = Depends(),
         status_filter: StatusFilterParams = Depends(),
         serialization: SerializationParams = Depends(),