Use sockets to update latest block/batch on home page

[maxaleks]

Description and Related Issue(s)

Resolves #3245

Checklist for PR author

• I have tested these changes locally.
• I added tests to cover any new functionality, following this guide
• Whenever I fix a bug, I include a regression test to ensure that the bug does not reappear silently.
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Note

Medium Risk
Introduces live socket-driven cache updates for homepage stats, which can cause stale/incorrect UI if event payloads or query keys don’t match expectations, but changes are localized to the homepage widgets.

Overview
Homepage stats now derive the Latest block value from the general:homepage_blocks endpoint (with a stub placeholder) instead of treating it as a "total blocks" metric, and the widget label is updated accordingly (including degraded/fallback UI and mocks).

Adds websocket subscriptions on the homepage stats panel to push real-time updates into the React Query cache for blocks:new_block and (for Arbitrum/zkEVM) latest batch events, with guardrails to disable sockets during placeholder/error states and to de-duplicate/sort incoming items.

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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[cursor]

Fallback value semantically mismatches "Latest block" label

Low Severity

When blocksQuery.data is an empty array (no blocks returned by API), the value falls back to statsData?.total_blocks?.value or apiData?.total_blocks, which represent the total block count, not the latest block height. The label reads "Latest block" but the displayed number would be total blocks (off by one from the actual latest height). The falsy check on height also means block height 0 would incorrectly trigger this fallback path.

 

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