fix: reduce functions count to avoid Hobby plan limit

[0rlandoMG]

Problem

When deploying a fork to Vercel's Hobby (free) plan, the build fails with:

No more than 12 Serverless Functions can be added to a Deployment on the Hobby plan.

This happens even on a fresh, unmodified fork of the vercel branch.

Cause

In vercel.json, the functions block uses the glob pattern api/**/*.php:

"functions": {
  "api/**/*.php": {
    "runtime": "vercel-php@0.9.0"
  }
}

This causes every .php file under api/ to be deployed as its own separate serverless function — including internal library files that are never called directly over HTTP (cache.php, card.php, colors.php, generator.php, stats.php, themes.php, translations.php, whitelist.php, etc.). These files are only required by api/index.php; they aren't independent endpoints.

Looking at the routes section, only 3 files are actually routed to as endpoints:

• api/index.php
• api/demo/index.php
• api/demo/vercel-static.php

Counting each PHP file as a function pushes the total past the Hobby plan's 12-function limit, blocking self-hosting for free-tier users — which contradicts the README's claim that Vercel is "free and easy to set up."

Fix

This PR narrows the functions glob to only the 3 files that are actually used as HTTP endpoints, matching what's declared in routes:

"functions": {
  "api/index.php": {
    "runtime": "vercel-php@0.9.0"
  },
  "api/demo/index.php": {
    "runtime": "vercel-php@0.9.0"
  },
  "api/demo/vercel-static.php": {
    "runtime": "vercel-php@0.9.0"
  }
}

All the other PHP files continue to work exactly as before — they're still required normally by index.php as plain PHP includes, they just stop being counted as separate serverless functions.

Testing

Tested by forking the vercel branch and deploying to a Vercel Hobby account:

• Before this change: build failed immediately with the 12-function limit error.
• After this change: deployment succeeds, function count drops to 3, and the streak card renders correctly with real GitHub data.