models: Remove payload re-exports to break import cycle

- remove payload-model re-exports from `pdfrest.models` to break the
  `models -> payloads -> _internal -> types -> models` import cycle
- keep payload models available through `pdfrest.models.payloads`
- update encryption and permissions-password unit tests to import payload models
  from `pdfrest.models.payloads` instead of `pdfrest.models`

Validation:
- `uv run ruff check src/pdfrest/models/__init__.py tests/test_encrypt_pdf.py tests/test_permissions_password.py`
- `uv run basedpyright src/pdfrest/models/__init__.py src/pdfrest/models/payloads.py src/pdfrest/models/_internal.py src/pdfrest/types/__init__.py src/pdfrest/types/public.py tests/test_encrypt_pdf.py tests/test_permissions_password.py`
- `uv run pytest -n auto --maxschedchunk 2 tests/test_encrypt_pdf.py tests/test_permissions_password.py`

Assisted-by: Codex

Author: datalogics-cgreen

src/pdfrest/models/__init__.py

@@ -1,9 +1,3 @@
-from .payloads import (
-    PdfDecryptPayload,
-    PdfEncryptPayload,
-    PdfRestrictPayload,
-    PdfUnrestrictPayload,
-)
 from .public import (
     PdfRestDeletionResponse,
     PdfRestErrorResponse,
@@ -18,16 +12,12 @@
 )
 
 __all__ = [
-    "PdfDecryptPayload",
-    "PdfEncryptPayload",
     "PdfRestDeletionResponse",
     "PdfRestErrorResponse",
     "PdfRestFile",
     "PdfRestFileBasedResponse",
     "PdfRestFileID",
     "PdfRestInfoResponse",
-    "PdfRestrictPayload",
-    "PdfUnrestrictPayload",
     "SummarizePdfTextResponse",
     "TranslatePdfTextFileResponse",
     "TranslatePdfTextResponse",

tests/test_encrypt_pdf.py

@@ -9,12 +9,11 @@
 
 from pdfrest import AsyncPdfRestClient, PdfRestClient
 from pdfrest.models import (
-    PdfDecryptPayload,
-    PdfEncryptPayload,
     PdfRestFile,
     PdfRestFileBasedResponse,
     PdfRestFileID,
 )
+from pdfrest.models.payloads import PdfDecryptPayload, PdfEncryptPayload
 
 from .graphics_test_helpers import (
     ASYNC_API_KEY,

tests/test_permissions_password.py

@@ -12,9 +12,8 @@
     PdfRestFile,
     PdfRestFileBasedResponse,
     PdfRestFileID,
-    PdfRestrictPayload,
-    PdfUnrestrictPayload,
 )
+from pdfrest.models.payloads import PdfRestrictPayload, PdfUnrestrictPayload
 from pdfrest.types import PdfRestriction
 
 from .graphics_test_helpers import (