fix: address PR review feedback and fix CI test failures

- Revert default transport to streamable-http (not a breaking change)
- Extract AVAILABLE_APPS constant to server/__init__.py (DRY)
- Wrap get_stdio_mcp ValueError in click.ClickException for clean errors
- Fix test_stdio.py: call _reload_config() so dynaconf sees env changes
- Use lazy %-style logging in stdio.py
- Add private API comments in test assertions
- Derive --enable-app CLI choices from AVAILABLE_APPS
- README: show explicit --transport stdio in uvx examples

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/server/__init__.py

@@ -1,3 +1,5 @@
+from typing import Callable
+
 from .calendar import configure_calendar_tools
 from .collectives import configure_collectives_tools
 from .contacts import configure_contacts_tools
@@ -10,7 +12,25 @@ from .sharing import configure_sharing_tools
 from .tables import configure_tables_tools
 from .webdav import configure_webdav_tools
 
+# Canonical mapping of app name → tool registration function.
+# Used by app.py (HTTP), stdio.py (stdio), and cli.py (--enable-app choices).
+# Semantic search is excluded here because it is a cross-app feature gated
+# by VECTOR_SYNC_ENABLED, not an individual Nextcloud app.
+AVAILABLE_APPS: dict[str, Callable] = {
+    "notes": configure_notes_tools,
+    "tables": configure_tables_tools,
+    "webdav": configure_webdav_tools,
+    "sharing": configure_sharing_tools,
+    "calendar": configure_calendar_tools,
+    "collectives": configure_collectives_tools,
+    "contacts": configure_contacts_tools,
+    "cookbook": configure_cookbook_tools,
+    "deck": configure_deck_tools,
+    "news": configure_news_tools,
+}
+
 __all__ = [
+    "AVAILABLE_APPS",
     "configure_calendar_tools",
     "configure_collectives_tools",
     "configure_contacts_tools",