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/components/helpcenter/HelpCenterMenuContent.vue

@@ -33,7 +33,7 @@
           <span class="menu-label">{{ menuItem.label }}</span>
           <i
             v-if="menuItem.showExternalIcon"
-            class="icon-[lucide--external-link] text-primary w-4 h-4 ml-auto"
+            class="icon-[lucide--external-link] text-primary size-4 ml-auto"
           />
           <i
             v-if="menuItem.key === 'more'"
@@ -88,7 +88,7 @@
       data-testid="whats-new-section"
     >
       <h3
-        class="section-description flex items-center gap-2.5 self-stretch px-8 pt-2 pb-2"
+        class="section-description flex items-center gap-2.5 self-stretch px-8 py-2"
       >
         {{ $t('helpCenter.whatsNew') }}
       </h3>