feat(frontend/marketplace): polish creator dashboard + redesign edit modal (#13083)

## Why

While reviewing /settings/creator-dashboard live, a few rough edges
showed up: approved agents had no easy way to jump to the marketplace
listing, pagination had only Prev/Next so navigating large submission
sets was slow, sort changes felt instant-but-silent, the first thumbnail
was hard to remove, image upload had no loading state, and the
edit-submission modal still used the old flat-form layout (the publish
flow already moved to the cleaner accordion design).

## What

- **Approved → marketplace links**: the agent name is now a `<Link>` to
`/marketplace/agent/{username}/{slug}` for approved submissions, and the
row dropdown gains a "View on marketplace" item.
- **Pagination**: sliding 5-page window of numeric buttons (centered on
`current_page`, clamped at the ends), keeping Prev/Next.
- **Sort feedback**: short transition flag + React-Query `isFetching`
drive an "Updating" spinner next to the section title.
- **Thumbnail fixes**: first-image remove button is bigger, has `z-30`,
`stopPropagation`; Add image button shows a spinner + "Uploading" while
the upload is in flight.
- **Edit submission modal**: rebuilt to match the publish step-2 design
— amber "Update note" card + Listing basics / Thumbnails / Experience
details accordion sections with per-section error/complete indicators.

## How

- New `creatorUsername` from `useGetV2GetUserProfile` flows through
`useCreatorDashboardPage → SubmissionsList/MobileSubmissionsList →
SubmissionItem/MobileSubmissionItem`, and `useSubmissionItem` derives
`marketplaceUrl` only when status is APPROVED + username + slug are
present.
- `Pagination` gains a `getVisiblePages(current, total)` helper that
returns up to 5 consecutive page numbers, anchored around the current
page.
- `useCreatorDashboardPage` keeps an `isSortingTransition` flag flipped
on for 400ms on every filter/sort change; the existing `isFetching` is
OR'd with it so the spinner also fires on pure client-side sort.
- `ThumbnailImages` accepts the new `isUploading` flag from
`useThumbnailImages`; the remove button is hoisted above its sibling
select button.
- `EditAgentForm` is rewritten to use `Accordion`,
`CharCountedTextarea`, and `ThumbnailImages` from the publish flow —
same hooks and schema as before, just the new layout.

## Test plan

- [ ] `/settings/creator-dashboard` shows the agent name as a link for
approved submissions (opens marketplace in a new tab); pending/rejected
rows stay plain text.
- [ ] Row dropdown shows "View on marketplace" only for approved
submissions.
- [ ] Pagination renders up to 5 numeric buttons; clicking page 4 of 10
shows 2–6; clicking last page clamps to last-5; numbers receive
`aria-current=page` on the active button.
- [ ] Changing sort or filter briefly shows "Updating" with a spinner in
the submissions header.
- [ ] In the publish modal Thumbnails accordion, the first image can be
removed; clicking "Add image" during upload shows the "Uploading" loader
and the button is disabled.
- [ ] Edit submission modal renders the Update note card + 3 accordion
sections (Listing basics, Thumbnails, Experience details), and Cancel /
Update buttons work.

Unit tests added/updated:
- `Pagination.test.tsx` — sliding window, aria-current, numeric click.
- `ThumbnailImages.test.tsx` (new) — empty state, remove first/last,
upload, generate, generate without agentId, select, file change.
- `EditAgentModal.test.tsx` (new) — accordion sections render, Cancel
triggers `onClose`, null-submission guard.