fix(deck): address review — notesPath key, scopes, modernize types

PR #781 review round 1:

- 🔴 Fix notesPath key: the Notes API returns the folder under camelCase
  ``notesPath`` (see models/notes.py:43), but `deck_attach_note` was
  looking up snake_case ``notes_path`` and silently falling back to
  ``"Notes"``. Users with a non-default notes folder would have produced
  shares pointing at non-existent files (404 on click in Deck UI).

- 🔴 Add wire-through unit test that would have caught the above:
  extract `_resolve_note_attach_path(client, note_id)` as a testable
  helper that encapsulates the camelCase-key lookup. Three new tests:
  custom notesPath honored, missing key falls back to default, null
  category handled.

- 🟡 Modernize new fields on `DeckAttachmentExtendedData` to PEP 604
  (`X | None`) per CLAUDE.md.

- 🟡 Drop unnecessary string forward reference on
  `ListAttachmentsResponse.results` — DeckAttachment is defined earlier
  in the same module.

- 🟢 Move `pytestmark = pytest.mark.unit` to module level in
  test_sharing_client.py to match the convention in test_deck_server.py.

Per user request: `deck_attach_file` is now scoped `deck.write` +
``files.read`` (was just `deck.write`) so the generic file-share
permission story is consistent — only `deck_attach_note` keeps
`notes.read` since it specifically reads from the Notes app. Docstring
updated to emphasise the tool is generic over the user's Files
(PDFs/images/etc., not just markdown).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/models/deck.py

@@ -145,10 +145,10 @@ class DeckAttachmentExtendedData(BaseModel):
     mimetype: str
     info: Dict[str, str]
     # Populated for type="file" (Files share) attachments via FilesAppService.
-    path: Optional[str] = None
-    fileid: Optional[int] = None
-    hasPreview: Optional[bool] = None
-    permissions: Optional[int] = None
+    path: str | None = None
+    fileid: int | None = None
+    hasPreview: bool | None = None
+    permissions: int | None = None
 
 
 class DeckAttachment(BaseModel):
@@ -336,7 +336,7 @@ class AttachFileResponse(BaseResponse):
 class ListAttachmentsResponse(BaseResponse):
     """Response model for listing card attachments."""
 
-    results: list["DeckAttachment"] = Field(
+    results: list[DeckAttachment] = Field(
         description="Attachments on the card (both type='file' and type='deck_file')"
     )
     count: int = Field(description="Number of attachments returned")