fix(marketplace): prevent search tab switches from polluting browser history

[Yawen-1010]

Important

1. Make sure you have read our contribution guidelines
2. Ensure there is an associated issue and you have been assigned to it
3. Use the correct syntax to link this PR: Fixes #<issue number>.

Summary

On the marketplace, pressing the browser back button from All Templates (/search/templates) landed users on All Plugins (/search/plugins) instead of returning to the page that opened search (e.g. /templates).

Root cause: useSearchTab().handleChange in web/app/components/plugins/marketplace/atoms.ts always called router.push when switching the search tab. Because /search/plugins, /search/templates, etc. are distinct paths, every in-page tab switch added a new history entry — so back had to traverse those entries before leaving the search context.

Fix: distinguish entry from in-page navigation.

• When already on /search/*, switch tabs with router.replace — no extra history entry.
• When entering search from elsewhere (e.g. clicking "View More" on /templates), keep router.push — the prior page stays in history so back works.

After this change:

• /templates → search input → /search/all → click Templates tab → /search/templates → Back goes directly to /templates (previously required two back clicks).
• Existing flows that enter search from outside (View More, search submit) are unaffected.

Screenshots

Before	After
Back from /search/templates lands on /search/plugins	Back from /search/templates returns to /templates

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods