chore: organize relay docs and deployment artifacts - #119

The completed relay69 prototype remained alongside the production relay, while reusable service examples and the deployed KR reference shared one flat directory. This change removes the obsolete prototype source after porting its unique protocol and security regressions to the product suite, and separates reusable examples from instance-specific operations.

It also adds audience-based documentation indexes in English, Korean, Japanese, and Simplified Chinese, updates every moved link, and makes sdist contents explicit: current docs and reusable examples are included; prototype source, local build output, and KR operational files are excluded.

Validation:

• python -m unittest discover -s tests -v (423 passed, 5 optional/platform skips)
• SESSION_PEER_CONTROL_INTEGRATION=1 python -m unittest tests.test_control_integration -v (5 passed)
• product relay/docs focus suite (43 passed)
• npm ci && npm run typecheck && npm test && npm audit --omit=dev in control/ (69 passed, audit 0)
• wheel/sdist build and content assertions
• git diff --check

Closes #111