feat(ios): SQL Server (MSSQL) driver via FreeTDS

[datlechin]

Summary

• Adds SQL Server support to the iOS TableProMobile app via FreeTDS db-lib over TDS 7.4
• Introduces TableProMSSQLCore SPM target with neutral types (MSSQLRawResult, MSSQLColumnType, MSSQLDatetimeFormatter, MSSQLSchemaQueries) shared between iOS app and future plugin refactor
• Cross-compiles FreeTDS 1.4.22 for iOS arm64 (device + simulator) and macOS arm64+x86_64 into a unified FreeTDS.xcframework, uploaded to the libs-v1 release
• Reuses the existing SSLConfiguration model from main (PR "Required (skip verify)" SSL mode does not actually skip certificate verification for Redis connections #1247) for TLS settings; no MSSQL-specific encryption enum
• Fixes SQL Server dialect in the iOS data browser: bracket-quoted identifiers [name], OFFSET ... ROWS FETCH NEXT ... ROWS ONLY pagination, SELECT TOP 1 for cell value fetch
• Enables database and schema switching for MSSQL in the iOS toolbar
• Test plan: 7 integration tests against a Docker azure-sql-edge container exercise connect, query, schema browsing, transactions

Test plan

• swift test --filter TableProMSSQLCoreTests in Packages/TableProCore (34 unit tests pass)
• xcodebuild -project TableProMobile.xcodeproj -scheme TableProMobileTests test -only-testing:TableProMobileTests/MSSQLDriverTests (7 integration tests pass against Docker SQL Server)
• iOS app builds clean on simulator (iPhone 17 Pro, iOS 26.5)
• Manual smoke test: connect to local Docker SQL Server, browse tables/views, run queries, switch database
• CI build on PR

What's NOT in scope

• Desktop plugin's inline FreeTDSConnection is not refactored to use the new shared core. Follow-up PR can extract for code reuse.
• ConnectionFormView iOS UI does not yet expose SSL mode picker for MSSQL. Defaults to .disable from existing connection form. Follow-up PR can add MSSQL-specific UI controls.

Release artifact

• tablepro-libs-ios-v1.tar.gz re-uploaded to libs-v1 release: now contains FreeTDS.xcframework (macOS arm64+x86_64 universal, iOS arm64 device, iOS arm64 simulator) alongside the existing xcframeworks.