Pin vcpkg registry references

[huangminghuang]

Summary

• Pin the Microsoft default vcpkg registry reference to a commit that contains the repo's current default-registry overrides
• Pin the Wire custom vcpkg registry reference to match its configured baseline

Why

The failed CI job in #342 showed vcpkg fetching the Wire registry from HEAD:

Fetching registry information from https://github.com/wire-network/wire-vcpkg-registry (HEAD)...
error: boost does not exist

For Git registries, baseline anchors package versions, but reference controls which Git ref vcpkg uses to list available versions. Without reference, vcpkg defaults to the registry's moving HEAD, which can make old builds fail when the registry changes.

The default Microsoft registry is pinned to bc71aa640f89933294f16e004b212c7fd3183eed, because that commit includes the exact version database entries required by the current manifest overrides, including protobuf 6.33.4#1.

Closes #342

Verification

• jq empty vcpkg-configuration.json
• Verified the Wire registry commit exists and its baseline contains boost
• Verified Microsoft/vcpkg bc71aa640f89933294f16e004b212c7fd3183eed contains protobuf 6.33.4#1
• Ran vcpkg install --dry-run from a temporary manifest root with both registry references pinned; dependency resolution succeeded without the previous protobuf version-database error