refactor: rename shadowed `t` parameter in `maxMembersByTier` computed in PricingTableWorkspace.vue

## Summary

In `src/platform/workspace/components/PricingTableWorkspace.vue`, the `maxMembersByTier` computed property uses a `.map()` callback parameter named `t`, which shadows the `t` function imported from `useI18n()`:

```ts
const maxMembersByTier = computed(
() =>
Object.fromEntries(tiers.map((t) => [t.key, getMaxSeats(t.key)])) as Record<
CheckoutTierKey,
number
>
)
```

The callback currently only accesses tier properties, so it is safe today. However, if an i18n call is ever added inside the callback, it would silently call the tier object instead of the translation function.

## Proposed Fix

Rename the callback parameter from `t` to `tier` to eliminate the shadow risk:

```ts
const maxMembersByTier = computed(
() =>
Object.fromEntries(tiers.map((tier) => [tier.key, getMaxSeats(tier.key)])) as Record<
CheckoutTierKey,
number
>
)
```

## Context

- Raised in PR #9901: https://github.com/Comfy-Org/ComfyUI_frontend/pull/9901
- Comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/9901#discussion_r2945814515
- Requested by @christian-byrne

## Labels

refactor, non-blocking

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-10211-refactor-rename-shadowed-t-parameter-in-maxMembersByTier-computed-in-PricingTabl-3266d73d36508129ac14e01f52aa06b5) by [Unito](https://www.unito.io)