fix(talk): address remaining PR #741 reviewer feedback

Closes the seven outstanding items from the @claude review on PR #741:

1. Add empty `tests/client/talk/__init__.py` for pytest discovery parity
   with `tests/client/{collectives,news}/`.
2. Standardise boolean query params to integers — `includeStatus` was the
   string `"true"` in `list_conversations`/`list_participants` while every
   other flag (`noStatusUpdate`, `lookIntoFuture`, `setReadMarker`,
   `includeLastKnown`) used `1`/`0`.
3. Replace the `app:install || app:enable` chain in the spreed install hook
   with `app:install --keep-disabled --force || true; app:enable spreed`,
   so unrelated install failures surface as a clear "app not found" from
   `app:enable` rather than being silently masked.
4. Add `_validate_token()` (alphanumeric whitelist) and call it from all
   six TalkClient methods that interpolate the token into a URL path —
   defence-in-depth against pathological tokens reaching httpx.
5. Rename `TalkConversation.type` to `room_type` with `Field(alias="type")`
   and `populate_by_name=True`, so the field no longer shadows Python's
   builtin while preserving spreed's wire format on input. MCP responses
   now serialize `room_type` (field name) instead of `type`.
6. `mark_as_read` now passes `json=body or None` so the bodyless
   "mark everything as read" call doesn't send a spurious `{}` body and
   `Content-Type: application/json` header.
7. `_validate_message_text` rejects whitespace-only messages, not just
   empty strings.

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

nextcloud_mcp_server/server/talk.py

@@ -27,8 +27,10 @@ _MESSAGE_MAX_LENGTH = 32000
 
 
 def _validate_message_text(message: str) -> None:
-    if not message:
-        raise ValueError("Message text must not be empty")
+    # Reject both empty strings and whitespace-only strings — spreed
+    # would happily post the latter as a visually-blank message.
+    if not message or not message.strip():
+        raise ValueError("Message text must not be empty or whitespace-only")
     if len(message) > _MESSAGE_MAX_LENGTH:
         raise ValueError(
             f"Message too long: {len(message)} characters (max {_MESSAGE_MAX_LENGTH})"