Refactor: Move empty cart check earlier in checkout process

[seer-by-sentry]

Fixes ANDROID-19. The issue was that: Flask's checkout function attempts to use quantities before its definition, causing a NameError masked by generic exception handling.

Move the check for an empty cart to before the inventory dictionary is created. This avoids unnecessary processing when the cart is empty.

This fix was generated by Seer in Sentry, triggered by [email protected]. 👁️ Run ID: 1021202

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[sentry]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: flask/src/main.py

Function	Unhandled Issue
checkout	Exception: Error validating enough inventory for product ... Event Count: 110k
checkout	DatabaseConnectionError: get_inventory checkout Event Count: 84

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Project	Deployment	Preview	Comments	Updated (UTC)
empower	Ignored	Preview		Aug 26, 2025 1:27pm

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 26.40%. Comparing base (abd4d70) to head (328217d).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
flask/src/main.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1003   +/-   ##
=======================================
  Coverage   26.40%   26.40%           
=======================================
  Files          41       41           
  Lines        1106     1106           
  Branches      128      128           
=======================================
  Hits          292      292           
  Misses        791      791           
  Partials       23       23           

Flag	Coverage Δ
api	6.35% <0.00%> (ø)
frontend	42.23% <ø> (ø)

Components	Coverage Δ
checkout_module	6.35% <0.00%> (ø)
product_component	39.15% <ø> (ø)

Files with missing lines	Coverage Δ
flask/src/main.py	0.00% <0.00%> (ø)