Create workflow to publish the v7 sample app

[gpunto]

🎯 Goal

While the v7 branch is not merged into develop, we're going to publish its Compose sample as a separate app. Incidentally, we're also moving to a different Firebase project

🛠 Implementation details

• Add the google-services.json for the new project
• Create workflow to publish the sample on merges into v7 or on manual dispatch

🎨 UI Changes

None

🧪 Testing

Try running the workflow -> check if the apk was published via Firebase Distribution

☑️Contributor Checklist

General

• I have signed the Stream CLA (required)
• Assigned a person / code owner group (required)
• Thread with the PR link started in a respective Slack channel (#android-chat-core or #android-chat-ui) (required)
• PR is linked to the GitHub issue it resolves

Code & documentation

• Changelog is updated with client-facing changes
• New code is covered by unit tests
• Comparison screenshots added for visual changes
• Affected documentation updated (KDocs, docusaurus, tutorial)

☑️Reviewer Checklist

• UI Components sample runs & works
• Compose sample runs & works
• UI Changes correct (before & after images)
• Bugs validated (bugfixes)
• New feature tested and works
• Release notes and docs clearly describe changes
• All code we touched has new or updated KDocs
• Check the SDK Size Comparison table in the CI logs

🎉 GIF

Please provide a suitable gif that describes your work on this pull request

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	5.25 MB	5.25 MB	0.00 MB	🟢
stream-chat-android-offline	5.48 MB	5.48 MB	0.00 MB	🟢
stream-chat-android-ui-components	10.60 MB	10.60 MB	0.00 MB	🟢
stream-chat-android-compose	12.81 MB	12.81 MB	0.00 MB	🟢