chore: Simplify .gitignore to exclude all .env files except .example.env

- Use .env* pattern to catch all environment files
- Explicitly allow .example.env with negation pattern
- Removes need to list individual .env variants

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -24,11 +24,9 @@ npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
 
-# local env files
-.env
-.env*.local
-.env.test
-.prod.env
+# local env files (exclude all except .example.env)
+.env*
+!.example.env
 
 # vercel
 .vercel