Add kotlin-compose, java-xml example app and background upload support to existing kotlin-xml app

[rohit-fastpix]

FastPix Resumable Uploads SDK - Documentation PR

Documentation Changes

What Changed

• New documentation added
• Existing documentation updated
• Documentation errors fixed
• Code examples updated
• Links and references updated

Files Modified

• README.md
• docs/ files
• USAGE.md
• CONTRIBUTING.md
• Other: examples/README.md + per-example READMEs (kotlin-xml, kotlin-compose, java-xml);
  new example app modules; settings.gradle.kts; gradle/libs.versions.toml; .gitignore;

Summary

Added two new example apps and reorganized the existing one under examples/:

• Moved the existing Kotlin/XML sample to examples/kotlin-xml.
• Added examples/kotlin-compose (Kotlin + Jetpack Compose) and examples/java-xml (Java + XML).
• All three now demonstrate a resumable background upload: the uploader is held in an
  UploadManager singleton and driven by a foreground UploadService, so the upload keeps
  running when the app is backgrounded (progress shown in a notification). It is not persisted,
  so a process kill ends the upload.
• Credentials moved out of source into local.properties (gitignored), surfaced via BuildConfig.
• Manifest hardening on the examples: backup disabled (with data-extraction/backup rules),
  usesCleartextTraffic="false", and declared dataSync foreground-service type.
• Root README gained an Example apps section linking to each example; the Compose README
  links to FastPix/android-StreamGate as a fuller
  reference. Added a recursive build/ ignore and a Sonar cpd exclusion for examples/**.

Testing

• All code examples tested
• [] Links verified
• Grammar checked
• Formatting consistent

Review Checklist

• Content is accurate
• Code examples work
• Links are working
• Grammar is correct
• Formatting is consistent

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Ready for review!