fix eslint-plugin-tailwindcss config

[draylegend]

What's wrong

`eslint.config.ts` registers `eslint-plugin-tailwindcss` and its rules
(`classnames-order`, `no-arbitrary-value`, `no-custom-classname`,
`no-contradicting-classname`) but the setup is broken in two ways:

1. Missing required setting. The plugin's README states
   `settings.tailwindcss.cssConfigPath` is mandatory ("REQUIRED, as the
   default value may not work out-of-the-box") — it's not set anywhere in
   `eslint.config.ts`. Without it, the plugin guesses the Tailwind v4 CSS
   entry path itself, and guesses wrong: it looked for
   `apps/app/src/style.css` (singular) when the real file is
   `apps/app/src/styles.css` (plural). Any rule that needs the compiled
   theme (`no-arbitrary-value`, `no-custom-classname`,
   `classnames-order`) throws `ENOENT` the moment it actually runs against
   a classname.

2. Not wired to `.html` files. The tailwindcss plugin/rules only live in
   the `files: ['/*.ts', '/*.js']` block. This app's Angular templates
   are external `.html` files (e.g. `apps/app/src/app/app.html`), so that's
   where `class="..."` attributes actually live — but the rules never run
   there today. This currently masks bug update eslint-plugin-tailwindcss #1: nothing has crashed lint yet
   only because the rules never touch a real classname.

Confirmed by temporarily adding the plugin to a `**/*.html` block and
running `nx run app:lint` against a test template with
`class="p-[13px] hidden block text-red-500 not-a-real-class"` — it threw:

```
NX ENOENT: no such file or directory, open '...\apps\app\src\style.css'
Rule: "tailwindcss/no-custom-classname"
```

Note: the plugin does support Angular templates (visits the
`TextAttribute` node from `@angular-eslint/template-parser`, and its
default `attributes` setting already includes `class`, `className`,
`ngClass`, `@apply`), so no Angular-specific workaround is needed — just
correct config.

Fix

In `eslint.config.ts`:

• Add `settings: { tailwindcss: { cssConfigPath: './apps/app/src/styles.css' } }`
  to the block(s) using the tailwindcss plugin.
• Add the `tailwindcss` plugin + its 4 rules to the `files: ['**/*.html']`
  block (alongside the existing `@angular-eslint/template/attributes-order`
  rule).
• Re-verify with the same repro above (a test template with an arbitrary
  value + invalid classname) to confirm the rules fire instead of crashing.

[draylegend]

Correction to the suggested fix above, based on actually reproducing it:

eslint-plugin-tailwindcss doesn't resolve cssConfigPath relative to the workspace root or to eslint.config.ts's own location. It resolves relative to the nearest directory above the file being linted that contains an eslint.config.{js,mjs,cjs,ts,mts,cts} or package.json (see eslint-plugin-tailwindcss's internal Wt ()/le () helpers).

This repo has apps/app/eslint.config.ts (which just re-exports the root config) and apps/app/package.json. So for any file under apps/app/, that plugin walk stops at apps/app/, not the repo root.

Using the issue's suggested ./apps/app/src/styles.css reproduces a different ENOENT — the path gets doubled:

ENOENT: ...\apps\app\apps\app\src\styles.css

The correct value, given this repo's structure, is:

ts settings: { tailwindcss: { cssConfigPath: './src/styles.css' } }

Verified with the same repro (class=\"p-[13px] hidden block text-red-500 not-a-real-class\" in apps/app/src/app/app.html) — rules now fire (arbitrary-value, contradicting-classname, no-custom-classname, classnames-order) instead of throwing, and nx run app:lint passes clean on the unmodified repo.