Linux: add Microsoft SQL Server driver (tiberius)

[Seha16]

Summary

Add a Microsoft SQL Server driver to the Linux port, implementing the "MSSQL via tiberius" item from linux/ROADMAP.md. SQL Server connectivity exists on macOS via a plugin; this brings it to the Linux (Rust + GTK4) build as a statically-linked driver crate, consistent with the no-plugin-system decision (docs/decisions/0001).

What's implemented

• New crate crates/drivers/mssql (tablepro-driver-mssql) on tiberius (pure-Rust TDS) with rustls TLS (no OpenSSL).
• Full core::Connection surface: connect (SQL auth, encryption from use_tls, trust-cert), list_tables, fetch_columns (PK / IDENTITY / computed / default via sys catalog), fetch_rows (OFFSET … FETCH pagination), query / query_params, execute / execute_params, execute_in_transaction, fetch_indexes, fetch_foreign_keys, ping, close.
• TDS → Value mapping for all value variants; @P-style parameter binding; server errors mapped to DriverError (login-failed → AuthFailed).
• Core dialect/DDL (sql_dialect.rs, sql_ddl.rs) gain mssql arms: [bracket] quoting, @Pn placeholders, IDENTITY(1,1), sp_rename, ALTER COLUMN, DROP INDEX … ON, DROP CONSTRAINT. Other engines are byte-for-byte unchanged.
• Registered in the app; the registry-driven connection dialog shows "SQL Server" (default port 1433). Structure-tab type list + DDL transaction wrapping updated.

Testing

• Unit tests for type/default/error mapping and every dialect/DDL builder.
• Integration tests (testcontainers, #[ignore] behind Docker) passing against SQL Server 2022 (CU14): connect + introspection (PK/IDENTITY), all-types value roundtrip + parameter binding, OFFSET/FETCH pagination, error mapping.
• cargo build --workspace, cargo test --workspace --lib, cargo fmt --all -- --check, cargo clippy --all-targets -- -D warnings all clean on the pinned 1.93 toolchain.

Known limitations

• SQL Server authentication only (Windows/Kerberos auth is not modelled by ConnectOptions).
• Column reorder is unsupported (MySQL-only, matches existing gating); an ALTER COLUMN that changes only a default is a no-op (MSSQL named-constraint management deferred).
• XML columns surface as text; one connection per session, serialized by a mutex.