fix: remove unsafe restart action

[bradtraversy]

Summary

• Remove the Restart API, process relaunch logic, launch metadata, and frontend controls introduced in v0.1.2-rc.1.
• Preserve the existing Stop flow, including Windows taskkill support and platform-neutral Stop wording.
• Preserve the release pipeline, installers, Windows signing, and published prerelease history.

Root cause

PortDoc restarted the process listening on a port, but supervised development servers can expose a child process rather than the process supervisor. In live Linux testing, PortDoc left the watcher tree behind and launched a non-equivalent replacement attached to PortDoc's terminal. Generic relaunch is not safe without an explicit supervisor or project launch contract.

Impact

The dashboard returns to Stop-only service control. v0.1.2-rc.1 remains an immutable failed prerelease. A future background-management feature will be designed separately.

Validation

• cargo fmt --check
• cargo test (101 passed)
• cargo clippy -- -D warnings
• npm run lint in web/
• npm run build in web/
• Confirmed no Restart endpoint, symbols, UI copy, or built-bundle references remain
• Confirmed release files and Windows Stop paths remain unchanged

The pull request CI matrix should validate Ubuntu, macOS, and Windows before merge.