[eas-cli] Combine .env and EAS environment variables for deploy command

[kitten]

Why

This allows --environment to be combined with local .env files, outputting a warning when any variables conflict since EAS environment variables will take precedence.

How

• Update createManifestAsync to return manifest and conflicting variable names
• Always call getEnv and merge variables into the env object
• Output names when conflicts occurred

Test Plan

• Tested locally

[github-actions]

Subscribed to pull request

File Patterns	Mentions
**/*	@szdziedzic, @khamilowicz, @sjchmiela, @radoslawkrzemien

Generated by CodeMention

[github-actions]

Size Change: +3.04 kB (+0.01%)

Total Size: 53.4 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	53.4 MB	+3.04 kB (+0.01%)

_{compressed-size-action}

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.

Project coverage is 52.49%. Comparing base (a1d086f) to head (0be4a4f).

Files with missing lines	Patch %	Lines
packages/eas-cli/src/worker/assets.ts	0.00%	11 Missing ⚠️
packages/eas-cli/src/commands/worker/deploy.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2783      +/-   ##
==========================================
- Coverage   52.51%   52.49%   -0.01%     
==========================================
  Files         583      583              
  Lines       22582    22589       +7     
  Branches     4452     4454       +2     
==========================================
  Hits        11856    11856              
- Misses      10691    10698       +7     
  Partials       35       35              

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[github-actions]

✅ Thank you for adding the changelog entry!