Add authenticated management API and automatic stack updates

[RF1705]

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Description

This draft adds an authenticated management API intended for local integrations such as Home Assistant, together with image update detection and optional automatic stack updates.

The implementation is a clean port/rewrite of functionality proven in the finder39/dockge fork, adapted to the current louislam/dockge master instead of merging the fork history. It also includes OCI image version support contributed in RF1705/dockge.

Because this is a large new feature, the PR is intentionally opened as a draft for design discussion before being considered merge-ready.

Main changes

• API key management in Settings > Integrations
• Generate, enter, copy, replace, and revoke a key
• Existing stored keys are never returned to the browser
• DOCKGE_API_KEY remains available as a fallback
• Sensitive settings are redacted from debug logging
• Timing-safe X-API-Key authentication
• Local and multi-agent REST endpoints for agents, stacks, status, start, stop, restart, update, update checks, auto-update settings, bulk updates, scheduler, history, and system prune
• Server-level agent connections that remain available without an open browser session
• Image update detection using local Docker digests and remote skopeo inspection
• Optional OCI org.opencontainers.image.version exposure as imageVersion
• Per-stack auto-update switch in the stack UI
• Cron-based update scheduler with manual trigger
• Persisted update history and UI
• Server-Sent Events endpoint for integration refresh notifications
• Database migration for stack settings and update history

Scope note

Finder39's self-update sidecar/deployment mechanism is intentionally not included here. Updating the Dockge stack that is currently hosting the API has different failure and recovery semantics and should be reviewed as a separate change.

Type of change

• User interface (UI)
• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Checklist

• My code follows the style guidelines of this project
• I ran ESLint and other linters for modified files
• I have performed a self-review of my own code and tested it
• My changes generate no new warnings
• Automated integration tests still need to be added for Docker and registry interactions

Verification

• tsc --noEmit
• ESLint for all modified TypeScript/Vue files
• Full frontend production build with Vite
• git diff --check

Related projects

• https://github.com/finder39/dockge
• https://github.com/finder39/ha-dockge
• https://github.com/RF1705/dockge