chore: bump to 1.7.124-alpha ahead of the release run

Pre-bumped so the release gate compiles the test profile at the final
version — create-release bumps after the gate, so the gate would otherwise
run on the old version and the bump would invalidate the cache, timing out
cargo-test-weekly on the compile rather than the tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "archipelago"
-version = "1.7.123-alpha"
+version = "1.7.124-alpha"
 edition = "2021"
 description = "Archipelago Bitcoin Node OS - Native backend"
 authors = ["Archipelago Team"]