fix(dataprotection): record post-ready stage errors

[weicao]

Fixes #10617

Summary

• pass the PostReady stage to restore stage error handling
• inspect the condition that belongs to the failing restore stage
• cover a postReady-only fatal error without creating a PreparedData condition

Tests

• focused postReady fatal-error spec
• go test ./controllers/dataprotection -count=1
• go vet ./controllers/dataprotection
• git diff --check

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.85%. Comparing base (5a57a85) to head (33e81d2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10619      +/-   ##
==========================================
+ Coverage   63.75%   63.85%   +0.10%     
==========================================
  Files         520      520              
  Lines       62957    62961       +4     
==========================================
+ Hits        40138    40204      +66     
+ Misses      19201    19165      -36     
+ Partials     3618     3592      -26     

Flag	Coverage Δ
unittests	63.85% <100.00%> (+0.10%)	⬆️

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