feat(ranking): add public leaderboard

[Poooel]

Summary

• persist display names as public player identity and allow edits only from the profile page
• add a localized leaderboard with a top-three podium, top-ten table, and the current player position
• show ranked match totals for forfeits and no-contests
• remove obsolete in-game and browser-local display-name editing paths

Validation

• pnpm lint
• pnpm --filter @knucklebones/front build
• pnpm --filter @knucklebones/worker exec tsc --noEmit
• unit tests: 78 passed
• worker integration tests: 66 passed
• focused profile, leaderboard, room-name, identity-transfer, and ranked-statistics tests
• git diff --check

[cloudflare-workers-and-pages]

Deploying knucklebones with    Cloudflare Pages

Latest commit:	f74d015
Status:	✅  Deploy successful!
Preview URL:	https://2263796a.knucklebones-8ep.pages.dev
Branch Preview URL:	https://feat-ranked-leaderboard.knucklebones-8ep.pages.dev

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