fix(gateway): validate peer synchronization URLs

[kvinwang]

Problem

Peer synchronization URLs from persisted/configured gateway state were accepted without restricting scheme, credentials, or malformed host data. Synchronization could target an invalid or unintended endpoint and fail after state was committed.

Root cause and fix

Parse and validate peer URLs at the boundary, allowing only the supported secure form before storing or connecting.

Implementation

The branch records the following focused implementation work:

• fix(gateway): validate peer synchronization URLs

Changed paths:

• dstack/gateway/src/kv/mod.rs

Scope

This PR addresses one logical gateway finding. It intentionally excludes the acceptance-test infrastructure from #841 and unrelated product fixes from #840.

Dependency and merge order

This PR is based directly on master and has no parent dependency.

Verification

• git diff --check origin/master..origin/codex/fix-gateway-peer-sync-urls: passed.
• The declared base was verified as an ancestor of the PR head.
• Focused compile/check verification was run for the changed component where applicable; non-Rust packaging or configuration changes were reviewed against their exact branch delta.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.