feat: add guided Amazon account setup

[eshaffer321]

Summary

• add a first-class itemize amazon setup -account <name> login flow
• create and secure the persistent Chromium profile automatically
• lead Amazon help with setup and move low-level authentication flags into an advanced section
• point missing or expired accounts to the guided setup command
• require an explicit setup account to avoid overwriting configured defaults
• document setup and add focused regression coverage

Validation

• go test ./...
• go test ./... -race
• golangci-lint run --timeout=5m
• go vet ./...
• Amazon dry run (expected authentication failure after saved profiles were intentionally removed; confirmed new setup guidance)
• independent lightweight review completed with no remaining findings

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.23%. Comparing base (b986777) to head (435438f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #66      +/-   ##
==========================================
+ Coverage   60.53%   61.23%   +0.69%     
==========================================
  Files          46       46              
  Lines        5757     5837      +80     
==========================================
+ Hits         3485     3574      +89     
+ Misses       2042     2027      -15     
- Partials      230      236       +6     

Flag	Coverage Δ
unittests	61.23% <100.00%> (+0.69%)	⬆️

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

Files with missing lines	Coverage Δ
internal/adapters/providers/amazon/provider.go	79.06% <100.00%> (ø)

... and 3 files with indirect coverage changes

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