docs: add fast build and clean commands to contributing guide
- Added documentation for the `pnpm build:fast` command which uses Rust's fast-release profile to reduce compilation time
- Added explanation that fast builds disable optimization and LTO, resulting in larger but quicker builds
- Added documentation for the `pnpm clean` command to clean Rust build files
* doc: add more building details
Some friends said the build failed.
* chore: replace test url
replace default delay check URL, some user say that the delay numbers seen in CVR are very different from those in other software, and this default test result is not a valid reference.
