[codex] Reset frontend shell

[pcharbon70]

Summary

Reset the web frontend to a clean Phoenix root shell and remove the existing UI component/layout layer.

• remove the old HEEx component modules, LiveVue widgets, vendor browser helpers, and UI-specific LiveView tests
• keep the Phoenix root layout/document shell and route existing LiveViews through a small reset placeholder surface
• add a metagraph-webui-style frontend baseline with SaladUI/shadcn-vue dependencies, components.json, Vite aliases, Tailwind v4 tokens, and a minimal Vue registry
• remove DaisyUI/live_toast usage and unused lock entries

Impact

Existing routed frontend pages now render the reset placeholder while the new frontend is rebuilt. Backend routes and Phoenix root asset loading remain in place.

Validation

Passed:

• mix deps.unlock --check-unused
• mix assets.build
• mix frontend.verify
• mix compile --warnings-as-errors
• mix test test/jido_code_web
• touched-file mix format --check-formatted ...
• git diff --check

Known unrelated full-suite status:

• mix test currently fails with 21 backend failures in memory graph hardening, conversation runtime DateTime normalization, and project import state isolation paths.