Add response compression with brotli for API Gateway

[Smartdevs17]

Description

API responses are uncompressed. Implement brotli compression at API gateway level with gzip fallback.

Acceptance Criteria

• Brotli compression at API gateway
• Compression level configuration (1-11)
• Minimum response size for compression
• Cache-control header preservation
• Bandwidth reduction measurement (target: 70%)
• Client Accept-Encoding negotiation

Technical Scope

• api/src/middleware/
• infra/
• Edge: compression of already-compressed data, streaming response handling