Add bindings() method to browser logger

[RT1811]

Summary

Adds bindings() support to the browser logger to match the Node implementation.

• Adds bindings() to browser logger instances
• Preserves bindings inherited when child loggers are created
• Ensures later parent setBindings() calls do not affect existing children
• Keeps internal binding state separate from the public bindings() method
• Adds browser tests for bindings behavior

Fixes #1177

Testing

• Added test/browser-bindings.test.js
• Existing browser-set-bindings.test.js tests pass
• CI=1 npm test passes