feat(config): support large uploads with read header timeout

Disable default read and write timeouts (set to 0s) to prevent Go from
prematurely closing connections during large multi-GB uploads.

Introduce `WARPBOX_READ_HEADER_TIMEOUT` (defaulting to 15s) to protect
against slowloris-style attacks while still allowing long-running
uploads to complete. Update documentation and example configurations
accordingly.

SECURITY_PROXY.md

@@ -54,6 +54,24 @@ network edge, or set it to a value that does not include public clients. Direct
 public exposure is not recommended; use a reverse proxy for TLS and request
 normalization.
 
+## Large Uploads
+
+Multi-GB uploads must not use whole-body read/write deadlines. Keep these
+Warpbox values for production unless you intentionally want a hard wall-clock
+upload limit:
+
+```env
+WARPBOX_READ_HEADER_TIMEOUT=15s
+WARPBOX_READ_TIMEOUT=0s
+WARPBOX_WRITE_TIMEOUT=0s
+```
+
+`WARPBOX_READ_HEADER_TIMEOUT` protects request headers. `WARPBOX_READ_TIMEOUT`
+and `WARPBOX_WRITE_TIMEOUT` cover the whole upload/response lifetime in Go, so
+small values can cause browser errors such as `NS_ERROR_NET_INTERRUPT` during
+large transfers. Upload size, daily, storage, and box limits still enforce abuse
+controls independently of these timeout values.
+
 ## Ban Behavior
 
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