docs: enhance README (badges, architecture, quickstart)

[stukenov]

Summary

OSS marketing pass on the README — purely additive (15 insertions, 0 deletions). All existing content, structure, and voice are preserved; no functionality, commands, or sections were removed.

Changes

• Badge row added under the title: License (MIT), TypeScript, NestJS 11, Next.js 15, and CI status.
• One-line value prop added as a blockquote summarizing the platform (resumable TUS uploads, Bull-queued HLS transcoding, adaptive-bitrate player, NestJS API + Next.js admin panel).
• ## Related projects section added, linking the broadcast suite:
  • live-streaming-server
  • fast-tv-playout-core

Notes

• The architecture overview and quickstart already existed and accurately match the real code (NestJS panel/back, Next.js panel/front, Express player; TUS/@tus/server, Bull, S3, TypeORM, HLS), so they were left untouched.
• All documented run/build/test commands were verified against the real package.json scripts — nothing invented.
• LICENSE not touched.

Marketing note: this PR improves first-impression and discoverability (scannable badges, a crisp value prop, and cross-links to the rest of the streaming suite) without changing any technical guidance.

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