fix: enable enforce-canonical-classes tailwind lint rule (#9427)

## Summary

Enable `better-tailwindcss/enforce-canonical-classes` lint rule and
auto-fix all 611 violations across 173 files. Stacked on #9417.

## Changes

- **What**: Simplify Tailwind classes to canonical forms via `eslint
--fix`:
  - `h-X w-X` → `size-X`
  - `overflow-x-hidden overflow-y-hidden` → `overflow-hidden`
  - and other canonical simplifications
- Enable `enforce-canonical-classes` as `'error'` in eslint config

## Review Focus

Mechanical auto-fix PR — all changes produced by `eslint --fix`. No
visual or behavioral changes; canonical forms are functionally
identical.

**Stack:** #9417 → **this PR** → PR 3 (class order)

Fixes #9300 (partial — 2 of 3 rules)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9427-fix-enable-enforce-canonical-classes-tailwind-lint-rule-31a6d73d365081a49340d7d4640ede45)
by [Unito](https://www.unito.io)

src/platform/cloud/onboarding/CloudSignupView.vue

@@ -3,7 +3,7 @@
     <div class="max-w-screen p-2 lg:w-96">
       <!-- Header -->
       <div class="mb-8 flex flex-col gap-4">
-        <h1 class="my-0 text-xl leading-normal font-medium">
+        <h1 class="my-0 text-xl/normal font-medium">
           {{ t('auth.signup.title') }}
         </h1>
         <p class="my-0 text-base">
@@ -50,7 +50,7 @@
 
           <Button
             type="button"
-            class="h-10 bg-[#2d2e32]"
+            class="h-10 bg-charcoal-500"
             variant="secondary"
             @click="signInWithGithub"
           >