feat: enhanced authentication logging for better debugging (fixes #22, #16)

- Added specific error reasons for auth failures: no_auth_header, invalid_auth_format, invalid_token
- Fixed AUTH_TOKEN_FILE support in Docker production stacks (issue #16)
- Added AUTH_TOKEN_FILE support to single-session HTTP server for consistency
- Enhanced security by removing token lengths from logs
- Added token trimming and empty token validation
- Updated Docker entrypoint to properly support AUTH_TOKEN_FILE
- Bumped version to 2.7.10

This improves debugging for mcp-remote authentication issues and enables
proper Docker secrets usage in production environments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docker/docker-entrypoint.sh

@@ -2,8 +2,14 @@
 set -e
 
 # Environment variable validation
-if [ "$MCP_MODE" = "http" ] && [ -z "$AUTH_TOKEN" ]; then
-    echo "ERROR: AUTH_TOKEN is required for HTTP mode"
+if [ "$MCP_MODE" = "http" ] && [ -z "$AUTH_TOKEN" ] && [ -z "$AUTH_TOKEN_FILE" ]; then
+    echo "ERROR: AUTH_TOKEN or AUTH_TOKEN_FILE is required for HTTP mode"
+    exit 1
+fi
+
+# Validate AUTH_TOKEN_FILE if provided
+if [ -n "$AUTH_TOKEN_FILE" ] && [ ! -f "$AUTH_TOKEN_FILE" ]; then
+    echo "ERROR: AUTH_TOKEN_FILE specified but file not found: $AUTH_TOKEN_FILE"
     exit 1
 fi