feat(add): preview well-known services with dry run

[jongio]

Closes #486

Summary

• add azd app add <service> --dry-run
• print the generated azure.yaml service block without writing the file
• include the preview in JSON output

Verification

• go test .\src\cmd\app\commands -run "Test(BuildServicePreview|RunAddDryRunDoesNotModifyAzureYaml|AddServiceToYaml|ServiceExistsInYaml)"
• mage test
• mage build

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 63.88889% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.93%. Comparing base (68b3cae) to head (4a5aec9).

Files with missing lines	Patch %	Lines
cli/src/cmd/app/commands/add.go	63.88%	9 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #489      +/-   ##
==========================================
+ Coverage   60.77%   60.93%   +0.15%     
==========================================
  Files         223      223              
  Lines       28527    28563      +36     
==========================================
+ Hits        17337    17404      +67     
+ Misses      10010     9968      -42     
- Partials     1180     1191      +11     

Flag	Coverage Δ
unittests	60.93% <63.88%> (+0.15%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cli/src/cmd/app/commands/add.go	55.93% <63.88%> (+20.82%)	⬆️

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[github-actions]

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Live Preview: https://jongio.github.io/azd-app/pr/489/

One-Line Install (Recommended)

PowerShell (Windows):

iex "& { $(irm https://raw.githubusercontent.com/jongio/azd-app/main/cli/scripts/install-pr.ps1) } -PrNumber 489 -Version 0.19.5-pr489"

Bash (macOS/Linux):

curl -fsSL https://raw.githubusercontent.com/jongio/azd-app/main/cli/scripts/install-pr.sh | bash -s 489 0.19.5-pr489

Uninstall

When you're done testing:

PowerShell (Windows):

iex "& { $(irm https://raw.githubusercontent.com/jongio/azd-app/main/cli/scripts/uninstall-pr.ps1) } -PrNumber 489"

Bash (macOS/Linux):

curl -fsSL https://raw.githubusercontent.com/jongio/azd-app/main/cli/scripts/uninstall-pr.sh | bash -s 489

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Build Info:

• Version: 0.19.5-pr489
• Commit: 4a5aec9
• Release: View pre-release

What to Test:
Please review the PR description and test the changes described there.