Add native named parameter binding

[lovasoa]

Summary

• add exact-token bind_named() support for native named-parameter databases
• implement SQLite and MSSQL argument binding without SQL rewriting or hashmaps
• reject mixing named and positional parameters in one query
• extend QueryBuilder and document the API

Validation

• cargo check --features all,rustls
• focused SQLite named-parameter and positional multi-statement tests
• MSSQL argument unit tests
• full SQLite test run with DATABASE_URL=sqlite::memory:: 28 passed, 2 failed due to existing schema/pragma setup assumptions (tweet table and pragma metadata)

Clippy remains blocked by existing warnings outside this change.