fix: migrate static UI to Tailwind v4

[JackSpiece]

Summary

Closes #119.

This migrates the current static Vue UI from the old Tailwind CDN script to the Tailwind v4 browser build. It also updates the old opacity utility pattern to v4 slash opacity classes and moves the custom theme from tailwind.config into a type="text/tailwindcss" @theme block, which the v4 browser build compiles directly.

I kept the patch scoped to the current static UI files on main, without touching the old ui/ paths from earlier attempts.

Validation

• python -m py_compile agentic_security/routes/static.py
• git diff --check
• Grep check for removed patterns: bg-opacity, border-opacity, text-opacity, placeholder-opacity, divide-opacity, ring-opacity, tailwind.config, cdn.tailwindcss.com, and broken /NN opacity fragments
• Confirmed https://cdn.jsdelivr.net/npm/@tailwindcss/browser@4 resolves with HTTP 200 and currently serves @tailwindcss/browser@4.3.0
• Ran a lightweight Node fake-DOM smoke check against the downloaded browser bundle and the actual head.html theme block to verify generated selectors for bg-dark-bg, text-dark-text, font-technopollas, rounded-lg, slash-opacity colors, and hover slash-opacity colors