Remove 11 unnecessary CI workflows (#5)

Removed template boilerplate workflows not relevant to boj-server:
ts-blocker, npm-bun-blocker, guix-nix-policy, jekyll-gh-pages,
jekyll, rsr-antipattern, scorecard-enforcer, wellknown-enforcement,
workflow-linter, security-policy, instant-sync.

Kept: zig-test, release, mirror, hypatia-scan, codeql, scorecard,
quality, secret-scanner.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: hyperpolymath