test(cells): add S3 transfer e2e coverage [WPB-26729]

[MohamadJaara]

https://wearezeta.atlassian.net/browse/WPB-26729

Goal

Add focused Android E2E coverage for the Kalium Cells S3 transport refactor without exercising the full Shared Drive feature set.

Changes

• provision Cells-enabled teams and conversations in the E2E backend setup
• verify a regular 2 MiB upload and receiver-side download with exact size and SHA-256 checks
• verify the multipart boundary with a 100 MiB + 1 byte file
• cover direct-download cancellation, partial-file cleanup, retry, and final checksum verification
• reuse and extend the existing UI Automator page objects, DocumentsUI flow, and test-support file helpers

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.40%. Comparing base (ba5c450) to head (43d0900).
⚠️ Report is 8 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5048      +/-   ##
===========================================
- Coverage    49.52%   49.40%   -0.12%     
===========================================
  Files          651      653       +2     
  Lines        23458    23598     +140     
  Branches      3602     3625      +23     
===========================================
+ Hits         11617    11659      +42     
- Misses       10767    10861      +94     
- Partials      1074     1078       +4     

see 10 files with indirect coverage changes

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