feat: Add typed qualifier to runtime path + custom qualifier to precompiled path

[harrytmthy]

Summary

This PR adds custom qualifier annotation support to Stitch's precompiled path, including field injection, constructor injection, @Provides, @Binds, dependency resolution, and generated Injector.get(...) support.

Implementation Details

Qualifier resolution is now derived directly from each annotated symbol instead of relying on a predefined qualifier scan phase, which allows Stitch to recognize custom marker qualifiers annotated with @Qualifier, even when they come from other modules. This PR also adds validation to reject multiple qualifiers on the same symbol, introduces Qualifier.Custom in the KSP model, and updates generated injectors to resolve custom qualifiers through both named(...) and the new type-based typed(...) runtime qualifier. Together, these changes make common Dagger and Hilt qualifier patterns such as @Production and @Staging work end-to-end in Stitch's precompiled path.

Closes #203