feat(gateway): add configurable response write timeout

[gitsrc]

This commit introduces a configurable response write timeout for the IPFS gateway.
The timeout can be set via the ResponseWriteTimeout field in the gateway configuration.
If not set, a default timeout of 30 seconds is applied.

The implementation includes:

• A new timeoutResponseWriter struct that wraps the standard http.ResponseWriter
  and enforces the timeout.
• A middleware function WithResponseWriteTimeout that applies the timeout logic
  to the HTTP handler chain.
• Comprehensive unit tests to verify the timeout behavior under various scenarios.

The timeout ensures that slow or unresponsive clients do not indefinitely hold
server resources, improving the overall reliability and stability of the gateway.

This change also attempts to address the issue described in #679
by providing a mechanism to handle slow or stuck HTTP responses more gracefully.

[skip changelog]

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[gammazero]

This addresses what was asked for in #679 but I think that if can live without the ask, "Every time data is written successfully, the timer is reset" then things can be much simpler. For example: #818

[gitsrc]

OK, I understand, it would be cleaner to set a uniform timeout.

This addresses what was asked for in #679 but I think that if can live without the ask, "Every time data is written successfully, the timer is reset" then things can be much simpler. For example: #818