fix: clean tauri appimage cache path

[AnrokX]

Summary

• clean the stale AppImage bundle directory using the resolved cargo target root before Tauri builds
• write PR review automation logs under the runtime working directory logs folder
• drop the unfinished Linux packaging experiment so the branch only contains commit-ready changes

Test plan

• node --check scripts/tauri/prepare-backend-resources.js
• node --check scripts/tauri/run-tauri-build.js
• node --check server/prReviewAutomationService.js
• node scripts/tauri/run-tauri-build.js --dry-run
• git diff --check