Migrate coil-transformations and update to Coil 3.x

[theJawnnybot]

Summary

Applied the open-source-library-migration.md checklist and updated Coil to 3.x.

Build/toolchain

• Java 17
• Gradle 9.3.1 (wrapper + scripts refreshed)
• AGP 9.1.0
• Kotlin 2.3.10 version catalog update
• Updated dependencies to current versions, including Coil 3.2.0

Publishing

• Switched publishing host to Central Portal:
  • publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
• Kept release signing gate (RELEASE_SIGNING_ENABLED)
• Patch bump in gradle.properties to VERSION_NAME=3.0.8

CI/CD

• Modernized CI workflow and wrapper validation action
• Updated release workflow to use:
  • MAVEN_CENTRAL_USERNAME
  • MAVEN_CENTRAL_PASSWORD
  • SIGNING_PRIVATE_KEY
  • SIGNING_PASSWORD
• Release now uses tag arg override (no file mutation):
  • -PVERSION_NAME="${GITHUB_REF_NAME}"

Docs/cleanup

• Removed .jitpack.yml
• Updated README to Maven Central badge + dependency coordinates
• Updated README preview link from master to main

Validation

• ./gradlew build ✅