⚡ Bolt: Implement module-level cache for BlogApp data fetching

[schmug]

💡 What: Introduced a module-level cache (fetchPromise and cachedPayload) in BlogApp.tsx.
🎯 Why: In the windowed UI architecture, components frequently mount and unmount when opened and closed. Previously, the app fetched /api/blog.json in a useEffect on every mount, causing redundant network requests and a visible loading state every time the user reopened the Blog app.
📊 Impact: Reduces network requests to exactly 1 per session for the Blog payload, resulting in instant loads on subsequent app opens.
🔬 Measurement: Verified with pnpm test and pnpm lint. The caching logic prevents unnecessary state transitions and network trips.

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PR created automatically by Jules for task 2658475653760629607 started by @schmug

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[schmug]

Superseded by #127 (merged to main), which consolidated the best of the duplicate Bolt/Sentinel/Palette scheduled-agent PRs into one reviewed change. Closing as duplicate.

[google-labs-jules]

Superseded by #127 (merged to main), which consolidated the best of the duplicate Bolt/Sentinel/Palette scheduled-agent PRs into one reviewed change. Closing as duplicate.

Understood. Acknowledging that this PR is a duplicate and superseded. Stopping work on this task.