feat(deck): add card comment tools

Expose four new MCP tools backed by existing DeckClient comment methods:

- deck_get_card_comments — list with limit/offset pagination
- deck_create_card_comment — top-level or threaded (via parent_id)
- deck_update_card_comment — author-only on the server
- deck_delete_card_comment — author-only, destructive, idempotent

Adds ListCardCommentsResponse and CardCommentOperationResponse models, and
extends the client unit tests to cover replies, deletion, pagination, and
the request shape for updates.

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

nextcloud_mcp_server/models/deck.py

@@ -280,3 +280,20 @@ class LabelOperationResponse(StatusResponse):
 
     label_id: int = Field(description="ID of the affected label")
     board_id: int = Field(description="ID of the board containing the label")
+
+
+# Comment Response Models
+
+
+class ListCardCommentsResponse(BaseResponse):
+    """Response model for listing card comments."""
+
+    results: list[DeckComment] = Field(description="List of card comments")
+    total: int = Field(description="Number of comments returned")
+
+
+class CardCommentOperationResponse(StatusResponse):
+    """Response model for card comment create/update/delete operations."""
+
+    card_id: int = Field(description="ID of the card the comment belongs to")
+    comment_id: int = Field(description="ID of the affected comment")