fix: cap advertised resumable chunk size to route limit

[rabble]

Summary

• cap advertised resumable chunk size to the configured upload-route body limit
• add a regression test proving the server never advertises a chunk larger than the route can accept
• document the new RESUMABLE_MAX_REQUEST_BODY_SIZE env var

Test Plan

• cargo test --manifest-path /Users/rabble/code/divine/divine-upload-server/.worktrees/fix-resumable-ingress-contract/Cargo.toml

[NotThatKindOfDrLiz]

Closing as superseded by PR #1 (5303eeb), plus follow-up fixes in PR #3 and PR #4. The docs and ignore changes from this branch are already on main, and the remaining code here is stale relative to the current resumable upload behavior.

[NotThatKindOfDrLiz]

Closing as superseded by PR #1 (5303eeb), plus follow-up fixes in PR #3 and PR #4. The docs and ignore changes from this branch are already on main, and the remaining code here is stale relative to the current resumable upload behavior.