Remove USSP support and harden GitHub sync (retries, attachments, snapshots)

[Povo-43]

Motivation

• Remove deprecated USSP dependency and simplify sync flow by moving snapshot and backup responsibilities fully to GitHub.
• Make GitHub uploads and downloads more robust against rate limits, concurrent updates and transient errors.
• Add support for syncing attachment blobs and reduce failed/duplicate uploads by SHA/base64 comparison and batching.

Description

• Removed USSP-related state/inputs/UX and deleted all ussp SDK usage and helper functions, and removed usspBaseUrl from state and UI.
• Added putGithubFileSafely, sleep and parseRateLimitResetMs to perform PUT retries with conflict handling, rate-limit backoff and sha-refresh logic.
• Converted parallel upload paths to use Promise.allSettled and log partial failures instead of failing whole batch, and reduced batch sizes for text and attachment uploads.
• Made text fetch/decode and per-file restores resilient with try/catch and logged warnings, and marked migrated legacy pieces with empty SHAs to avoid incorrect SHA assumptions.
• Reworked uploadRepoSnapshot to save snapshots to GitHub using putGithubFileSafely and wired auto-save to call it, with improved error logging and user toast on failure.
• Implemented syncAttachmentsToGithub to upload attachments from local DB, skip unchanged files by comparing remote base64 content, and perform batched uploads with retries.
• Minor UI changes: removed USSP controls from index.html and removed USSP favorite actions in app-ui.js, and added assetsIndex to startup diff checks and friendly labels.
• Improved error logging in fetchTextFileFromGithub and added safer remote-text comparison with warnings on decode failure.

Testing

• Ran automated lint and build checks via npm run lint and npm run build, both completed successfully.
• Executed automated smoke tests for GitHub sync paths (upload/download metadata, text backups and snapshots) against a test repo; uploads and snapshot saves completed with retry/backoff logic exercised and no fatal errors.
• Ran automated attachment upload tests covering base64 comparison and batched uploads, which passed and logged recoverable failures when simulated remote conflicts.

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Codex Task

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Project	Deployment	Actions	Updated (UTC)
v0-kaku-draft	Ready	Preview, Comment, Open in v0	May 19, 2026 10:12am