⚡ Add request timeout handling

[Gilfeather]

Description

Implement request timeout handling to prevent long-running requests from blocking the server.

Current Status - Partially Implemented

Model-level timeout exists but HTTP-level timeout handling is not implemented.

Already Implemented

• Model-level timeout in predict_batch_with_timeout method
• Timeout logging and monitoring
• Graceful timeout error handling at model level

Remaining Work

• Add configurable HTTP request timeout (default 30 seconds)
• Return HTTP 408 Request Timeout for exceeded requests
• Add timeout configuration to CLI arguments
• Add timeout middleware to Axum router
• Add tests for HTTP timeout behavior
• Update documentation with timeout information

Implementation Guidance

• Use tower::timeout::TimeoutLayer for HTTP-level timeouts
• Add --request-timeout CLI argument
• Consider different timeouts for different endpoints
• Integrate with existing model timeout for layered timeout handling

Estimated Difficulty

Easy - Half day (reduced due to existing timeout infrastructure)