- Add multi-browser build target support in build.js for Chrome and Firefox. - Generate Firefox Manifest V3 with browser_specific_settings (Gecko ID) and background scripts. - Normalize script injection paths in chrome-api.ts to support Firefox browser.scripting relative path rules. - Add getExtensionAPI helper in boot.ts for cross-browser extension URL resolution. - Safely handle isAllowedFileSchemeAccess in sidebar-injector.ts across Gecko and Chromium. - Fix Uint8Array type error when loading secretKey from localStorage in nostr-settings.ts. - Add Makefile with build, dev, lint-firefox, and multi-browser packaging targets.