Stream Cog file outputs from disk

[gurdasnijor]

Summary

• stream Path/File outputs from disk through reqwest instead of reading them into a Vec first
• send the known Content-Length and remove the 25-second whole-upload timeout
• retain buffering only for oversized JSON and data-URI fallback paths

Validation

• mise run fmt:rust
• mise run lint:rust
• mise run test:rust (223 passed)