feat: Whitelist-based asset filtering and -aw flag

[felix9743]

• Branch: feat/assets-whitelist
• Goal: Make assets hiding more robust by using a strict whitelist of page extensions rather than a fragile hardcoded blacklist, and allow users to dynamically allow specific extensions from the CLI.
• Changes:
  • Replaced the hardcoded assets blacklist with a clean pages/APIs whitelist (pagesWhitelist).
  • Added -aw / --assets-whitelist CLI flag to dynamically append custom extensions (e.g. .jsonc, .pdf) to the whitelist.