Prepare next version: 10.19.0-SNAPSHOT (#4035)

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> [!NOTE]
> **Low Risk**
> Mechanical version and docs-deploy path updates with no SDK behavior
changes.
> 
> **Overview**
> Bumps the development line from **10.18.0** to **`10.19.0-SNAPSHOT`**
across the repo so `main` can accept new work after the release.
> 
> **`VERSION_NAME`** in `gradle.properties`, **`.version`**, and
**`Config.frameworkVersion`** are updated together. CircleCI
**`docs-deploy`** now syncs Dokka output to
**`s3://purchases-docs/android/10.19.0-SNAPSHOT`**. Sample apps and
**`sdksizetesting`** pin the **`purchases`** catalog version to the new
snapshot.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
c80042f9dd87b02b08c76fcde0b636328813c79b. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->