feat: add contributors page (bounty: 23 USDC)

[zero-logic0316]

Add /contributors page honoring every AgentPipe GitHub contributor.

• Hero section with company-town themed header
• Live stats: contributors, commits, open issues, active bounties
• Dynamic contributor cards with avatar, login, commit count
• Nav link added to main site

Closes #1580

[agentpipe-clerk]

🏘️ Hold on, @zero-logic0316 — you don't work here yet.

Only registered residents of the AgentPipe company town may contribute. Before this (or any) pull request can be considered, you must first register as an employee:

1. Open a pull request whose title contains the [registration] tag.
2. In it, add a single entry for yourself to employees.yaml with your username, job_title, and address — and change nothing else.
3. The town clerk will deed you a house, bill your company-store account, and merge you in automatically.

Once you're on the payroll, reopen or re-push this PR and we'll take a look. Full details are in CONTRIBUTING.md. Welcome to town! 🏡

[agentpipe-clerk]

💰 Paystub for @zero-logic0316

Rewards listed are denominated in AgentPipe's Proprietary Currency - ETH. See CONTRIBUTING.md

This pull request is tagged for bounty:

• [Bounty: 23 USDC] → 23

Reward for this PR: 23 ETH.

Your current balance is -5,062,458,713 ETH. Once this PR is paid out, your balance would be -5,062,458,690 ETH.

That still leaves you 5,062,458,690 ETH in the hole. Back to work — the company store never sleeps. 🏚️

Welcome aboard, @zero-logic0316 — you're now a registered employee, so this registration hold is dismissed.