feat(talk): add MCP integration for Nextcloud Talk (spreed)

Adds 6 MCP tools so an LLM can read a user's Talk conversations and
post messages on their behalf, addressing the "read my chats and reply"
use case from issue #720:

  - talk_list_conversations
  - talk_get_conversation
  - talk_get_messages
  - talk_list_participants
  - talk_send_message    (auto-attaches a referenceId for retry dedup)
  - talk_mark_as_read

Edit/delete messages, reactions, threads, and call/session ops are
intentionally out of scope for this first PR.

The TalkClient also exposes create_conversation/delete_conversation
for the integration test fixture; these are not registered as MCP
tools. A post-installation hook enables spreed in the docker dev env
so the integration suite has a real Talk backend to talk to.

Closes #720

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

tests/conftest.py

@@ -38,7 +38,8 @@ DEFAULT_FULL_SCOPES = (
     "deck.read deck.write "
     "tables.read tables.write "
     "files.read files.write "
-    "sharing.read sharing.write"
+    "sharing.read sharing.write "
+    "talk.read talk.write"
 )
 
 # Read-only scopes (all read scopes across apps) - should match DEFAULT_FULL_SCOPES read portion
@@ -52,7 +53,8 @@ DEFAULT_READ_SCOPES = (
     "deck.read "
     "tables.read "
     "files.read "
-    "sharing.read"
+    "sharing.read "
+    "talk.read"
 )
 
 # Write-only scopes (all write scopes across apps) - should match DEFAULT_FULL_SCOPES write portion
@@ -66,7 +68,8 @@ DEFAULT_WRITE_SCOPES = (
     "deck.write "
     "tables.write "
     "files.write "
-    "sharing.write"
+    "sharing.write "
+    "talk.write"
 )
 
 
@@ -916,6 +919,43 @@ async def temporary_board_with_card(
                 logger.error(f"Unexpected error deleting temporary card {card.id}: {e}")
 
 
+@pytest.fixture
+async def temporary_conversation(nc_client: NextcloudClient):
+    """Create a temporary Talk conversation and clean it up after the test.
+
+    Yields a dict with the room ``token``, ``id``, and ``name``.
+    """
+    unique_suffix = uuid.uuid4().hex[:8]
+    room_name = f"MCP Test Room {unique_suffix}"
+    token = None
+
+    logger.info(f"Creating temporary Talk conversation: {room_name}")
+    try:
+        room = await nc_client.talk.create_conversation(room_name=room_name)
+        token = room.token
+        logger.info(f"Temporary Talk conversation created (token={token})")
+        yield {"token": token, "id": room.id, "name": room_name}
+
+    finally:
+        if token:
+            logger.info(f"Cleaning up temporary Talk conversation token={token}")
+            try:
+                await nc_client.talk.delete_conversation(token)
+                logger.info(f"Successfully deleted Talk conversation token={token}")
+            except HTTPStatusError as e:
+                if e.response.status_code not in [404, 403]:
+                    logger.error(f"HTTP error deleting Talk conversation {token}: {e}")
+                else:
+                    logger.warning(
+                        f"Talk conversation {token} already deleted or access denied "
+                        f"({e.response.status_code})."
+                    )
+            except Exception as e:
+                logger.error(
+                    f"Unexpected error deleting Talk conversation {token}: {e}"
+                )
+
+
 @pytest.fixture(scope="session")
 def shared_test_calendar_name():
     """Unique calendar name for the entire test session."""