Migrate Angular 4 to Angular 17 with standalone components

[nitrobass24]

Summary

• Upgrade Angular 4.2.4 to Angular 17.3.0 with standalone components
• Upgrade Bootstrap 4 to Bootstrap 5.3.3 (drops jQuery dependency)
• Replace Immutable.js with native TypeScript readonly + Object.freeze() (~60KB bundle reduction)
• Replace ngx-modialog with Angular CDK Dialog
• Convert all components to standalone (no NgModules)
• Use new @if/@for control flow syntax
• Update RxJS 5 to RxJS 7 pipe operators
• Update Dockerfiles to Node 20

Test plan

• Docker build succeeds
• Container starts and frontend loads at http://localhost:8800
• Verify SSE connection works with real seedbox
• Test file queue/stop/extract/delete operations
• Test settings save and persist
• Test autoqueue pattern management
• Visual comparison with old Angular 4 version

Rollback

Original Angular 4 code preserved in src/angular-v4/ if needed.

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