Add Crush coding agent integration

[nickclyde]

Summary

• Adds Charmbracelet Crush as a fifth option in the admin dashboard's "Other Integrations" panel, alongside Codex, OpenCode, OpenClaw, and Pi.
• New CrushIntegration writes ~/.config/crush/crush.json with an openai-compat provider pointed at the local oMLX server and binds the selected model to both the large and small Crush model slots.
• Wires crush_model through IntegrationSettings, the /admin/api/global-settings request/response, the dashboard Alpine state (crushCommand getter + save payload), and the omlx launch CLI help text. launch_command already dispatches via the INTEGRATIONS registry, so no CLI logic changes were needed.
• Adds status.integrations.crush_desc to all five locales (en/ja/ko/zh/zh-TW) with translations; ran scripts/normalize_i18n.py to keep key ordering aligned.
• TestCrushIntegration covers get_command, configure (new file / custom host / preserves existing / backup / invalid JSON / with+without limits / without model), and type. Bumps TestIntegrationRegistry to expect 5 entries and extends TestIntegrationSettings to cover crush_model.

Test plan

• pytest tests/test_integrations.py -v passes locally.
• Admin dashboard smoke-tested in browser: new Crush card renders, model select populates, command pane updates live, selection persists across reload.
• omlx launch crush --model <loaded-model> writes a valid ~/.config/crush/crush.json, preserves any pre-existing providers/LSP config (backup file produced), and the Crush TUI successfully hits the oMLX server.