Fix MSSQL Docker discovery on IPv4 loopback

[HerrLiljegren]

Summary

• use IPv4 loopback for Docker-discovered SQL Server connections
• cover the selected host through connection configuration
• keep Docker integration expectations aligned

Why

This surfaced while using sqlit to auto-connect to an Aspire-managed SQL Server container. Docker discovery found the mapped port and credentials, but localhost resolved to ::1 while SQL Server was published on IPv4 loopback, so the connection failed.

The change is MSSQL-specific. Manual connections and other providers are unchanged.

Tests

• regression test failed before the change and passed afterward
• affected Docker-discovery suite: 43 passed, 32 opt-in tests skipped
• focused Ruff and MyPy checks

Implementation and review were AI-assisted; the final diff and test evidence were manually reviewed.