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>

tests/test_cli.py

@@ -108,8 +108,6 @@ def test_cli_options_set_environment_variables(runner, clean_env, monkeypatch):
     _ = runner.invoke(
         run,
         [
-            "--transport",
-            "streamable-http",
             "--nextcloud-host",
             "https://test.example.com",
             "--nextcloud-username",
@@ -166,8 +164,6 @@ def test_cli_options_override_environment_variables(runner, monkeypatch):
     _ = runner.invoke(
         run,
         [
-            "--transport",
-            "streamable-http",
             "--nextcloud-host",
             "https://from-cli.example.com",
             "--nextcloud-username",
@@ -218,7 +214,7 @@ def test_environment_variables_used_when_cli_not_provided(runner, monkeypatch):
     monkeypatch.setattr("nextcloud_mcp_server.cli.get_app", mock_get_app)
 
     # Don't provide any CLI options - should use env vars
-    _ = runner.invoke(run, ["--transport", "streamable-http"])
+    _ = runner.invoke(run, [])
 
     # Verify env vars were used
     assert captured_env["NEXTCLOUD_HOST"] == "https://from-env.example.com"
@@ -250,7 +246,7 @@ def test_default_values(runner, clean_env, monkeypatch):
     monkeypatch.setattr("nextcloud_mcp_server.cli.get_app", mock_get_app)
 
     # Don't provide CLI options or env vars - should use defaults
-    _ = runner.invoke(run, ["--transport", "streamable-http"])
+    _ = runner.invoke(run, [])
 
     # Verify default values
     assert captured_env["NEXTCLOUD_OIDC_SCOPES"] == (
@@ -282,14 +278,12 @@ def test_oauth_token_type_case_normalization(runner, clean_env, monkeypatch):
     monkeypatch.setattr("nextcloud_mcp_server.cli.get_app", mock_get_app)
 
     # Test uppercase JWT
-    runner.invoke(run, ["--transport", "streamable-http", "--oauth-token-type", "JWT"])
+    runner.invoke(run, ["--oauth-token-type", "JWT"])
     assert captured_env["NEXTCLOUD_OIDC_TOKEN_TYPE"] in ["JWT", "jwt"]
 
     # Test mixed case Bearer
     captured_env.clear()
-    runner.invoke(
-        run, ["--transport", "streamable-http", "--oauth-token-type", "Bearer"]
-    )
+    runner.invoke(run, ["--oauth-token-type", "Bearer"])
     assert captured_env["NEXTCLOUD_OIDC_TOKEN_TYPE"] in ["Bearer", "bearer"]