fix: qualify aliased selected attributes

[elpete]

Closes #40

Issue review

Fit score: 9/10. Attribute-to-column translation is a core Quick promise and should continue to work when a select expression supplies an SQL alias, especially for asQuery() consumers.

Reasons for

• makes aliased projections consistent with ordinary Quick selects
• preserves entity property naming in direct query data
• fixes the shared qualifier rather than adding a one-off query workaround

Reasons against

• string parsing is limited to explicit AS, matching qb’s documented alias syntax
• complex expressions are still better expressed with qb raw expressions

Implementation

• recognizes case-insensitive source AS alias selections
• qualifies/translates only the source attribute
• preserves the caller-provided result alias

Reproduction

The public regression failed before the fix with MySQL Unknown column firstName in field list for select( "firstName AS firstName" ).asQuery( false ).

Validation

• focused AsQuerySpec: 4 passed, 0 failed, 0 errors
• full suite: 496 passed, 0 failed, 0 errors, 3 skipped
• box run-script format
• git diff --check
• qb dependency: 14.0.0-beta.3