Replace Bootstrap with Tailwind CSS + Alpine.js (#14)

## Summary

Replaces Bootstrap CSS/JS framework with Tailwind CSS v4 + Alpine.js, matching the µPaaS UI pattern.

## Changes

- **Removed Bootstrap** — all Bootstrap CSS/JS references removed from templates
- **Added Tailwind CSS v4** — `static/css/input.css` with Material Design inspired theme, compiled to `static/css/tailwind.css`
- **Added Alpine.js 3.14.9** — vendored as `static/js/alpine.min.js` for reactive UI components
- **Rewrote all templates** to use Tailwind utility classes:
  - `base.html` — new layout structure with footer, matches µPaaS pattern
  - `htmlheader.html` — Tailwind CSS link, `[x-cloak]` style
  - `navbar.html` — Alpine.js mobile menu toggle, responsive design
  - `index.html` — card-based dashboard with Tailwind classes
  - `login.html` — centered login form with Material Design styling
  - `profile.html` — clean profile layout
- **Added `make css` target** — compiles Tailwind CSS using standalone CLI
- **Component classes** in `input.css` — reusable `.btn-primary`, `.card`, `.input`, `.alert-error` etc.

## Testing

- `make fmt` ✅
- `make check` (fmt-check, lint, test, build) ✅
- `docker build .` ✅

closes #4

Co-authored-by: user <user@Mac.lan guest wan>
Reviewed-on: #14
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

templates/htmlheader.html

@@ -2,7 +2,7 @@
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>{{block "title" .}}Webhooker{{end}}</title>
-<link href="/s/vendor/bootstrap/css/bootstrap.min.css" rel="stylesheet">
-<link href="/s/css/style.css" rel="stylesheet">
+<link rel="stylesheet" href="/s/css/tailwind.css">
+<style>[x-cloak] { display: none !important; }</style>
 {{block "head" .}}{{end}}
-{{end}} 
+{{end}}