fix: broken support for custom appProjectName in Gradle Plugin

[artus9033]

Summary

This PR resolves the problem experienced in #260:

• fixes the Gradle plugin to invoke RNSourceSets::configure from an afterEvaluate block - otherwise, the extension's config fields are not set and carry default values
• uses the appProjectName field from GP's extensions to dynamically resolve task name in VariantProcessor (which so far used a hardcoded :app:... task path)

Test plan

CI green

[Copilot]

Pull request overview

Fixes Gradle plugin behavior when the consuming app module is not named app, ensuring the plugin reads the configured reactBrownfield extension values before configuring source sets and wiring variant tasks.

Changes:

• Invoke RNSourceSets.configure(...) from an afterEvaluate block so extension configuration is applied.
• Use the configured appProjectName when wiring the createBundle...JsAndAssets dependency for release variants.
• Add a changeset to publish the fix as a patch.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
gradle-plugins/react/brownfield/src/main/kotlin/com/callstack/react/brownfield/processors/VariantProcessor.kt	Use extension appProjectName instead of hardcoded :app: when depending on bundling task.
gradle-plugins/react/brownfield/src/main/kotlin/com/callstack/react/brownfield/plugin/RNBrownfieldPlugin.kt	Delay RNSourceSets.configure until afterEvaluate so extension values are finalized.
.changeset/crisp-animals-drive.md	Patch release notes for both packages.

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