release: promote v4.1.2 to main

[zelentsov-dev]

Release

• promote the audited App Store Connect API 4.4.1 contract completion from develop
• ship exact mutation outcome semantics, strict input validation, sparse response fidelity, and expanded contract coverage
• set server and Mint documentation version to 4.1.2

Verified on develop

• 1,845 Swift tests passed
• release build passed with zero compiler warnings
• strict App Store Connect OpenAPI 4.4.1 operation contract passed
• 502 public MCP tools remain available