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/input/MultiSelect.vue

@@ -46,7 +46,7 @@
       // Overlay & list visuals unchanged
       overlay: {
         class: cn(
-          'mt-2 rounded-lg py-2 px-2',
+          'mt-2 rounded-lg p-2',
           'bg-base-background',
           'text-base-foreground',
           'border border-solid border-border-default'
@@ -135,7 +135,7 @@
       </span>
       <span
         v-if="selectedCount > 0"
-        class="pointer-events-none absolute -top-2 -right-2 z-10 flex h-5 w-5 items-center justify-center rounded-full bg-primary-background text-xs font-semibold text-base-foreground"
+        class="pointer-events-none absolute -top-2 -right-2 z-10 flex size-5 items-center justify-center rounded-full bg-primary-background text-xs font-semibold text-base-foreground"
       >
         {{ selectedCount }}
       </span>