feat(debug-tool): expose dev URL pipe methods

[Huxpro]

Summary

• Expose debugtool.getDevUrl and debugtool.setDevUrl on Android and iOS so Lynx Settings can read and persist the debug server URL.
• getDevUrl returns the persisted URL (or an empty value when unset); setDevUrl validates and persists HTTP(S) URLs.

Validation

• Android: debug-tool tests passed, and the Android debug app build succeeded.
• iOS: the full Simulator build succeeded.
• Android SG1 Lynx Sandbox: Settings loaded without a pipe error; setting http://10.0.2.2:5969/ succeeded, and shared_prefs/sparkling_debug_tool.xml persisted it.
• iOS: Settings loaded without a pipe error.

Review

Requesting reviews from YJ-Hao, dirtmelon, and LittleGru because this change spans Android and iOS.

Fixes #85