feat: add release plan collaboration and versioned diffs

[huanghongbo-hhb]

Summary

• Add section-level collaboration state for release plan editing so users can see who is editing the same area.
• Add per-save release plan versions and version diff details so operation logs can show the exact configuration changes from each verb save.
• Add lightweight before/after snapshots for release job execution actions so retry/execute/skip logs can show status transitions.

Why

• Release plan users need Jira-like change records that show what changed after each save.
• When multiple users edit the same release plan, the UI needs backend state to warn that another user is editing the same section.

Main Changes

• Store active editing sessions in Redis with WebSocket snapshots grouped by section, including metadata, approval, and job:<jobID>.
• Generate one release plan version for each successful verb update and attach the resulting version to the corresponding operation log.
• Store section-level input snapshots instead of full release plan snapshots, then calculate diff from the saved before/after snapshots.
• Mask sensitive values based on existing workflow/keyvault sensitivity metadata and collapse large text fields to a changed marker.
• Add diff APIs, release plan version storage, log version fields, and lightweight execution-action snapshots.

Risk / Compatibility

• Existing verb + spec update requests remain compatible; session_id is no longer required for saving and is only used by collaboration WebSocket messages.
• This adds a release plan version collection and new diff/collaboration APIs, but stores only section input snapshots to avoid full-plan snapshot growth.
• Collaboration state is Redis-backed with TTL, so abnormal client exits may leave editing hints visible until the session expires.

Test

• UAT verified update_name creates a new version and returns metadata diff.
• UAT verified update_approval creates a new version and returns approval diff.
• UAT verified update_release_job for text jobs returns job-level diff with large text markers.
• UAT verified collaboration WebSocket join, heartbeat, leave, same-section editors, different-section grouping, and username display.
• UAT verified retry log records lightweight before/after state from failed to running.

Contact

• Contact: huanghongbo@koderover.com

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