fix(dataprotection): reject invalid restore target port

[weicao]

Fixes #10615

Related backup-side fix: #10612

What this PR does

• stops restore post-ready Jobs from silently falling back to the first pod port when an explicit named target port is missing
• propagates the lookup error before a Job is built
• preserves the legal default first-port behavior when no target ContainerPort is specified
• preserves explicit connection credential PortKey precedence

Tests

• focused restore target-port regression test
• full pkg/dataprotection/restore package with envtest 1.26.1
• full package with race detector
• go vet ./pkg/dataprotection/restore
• git diff --check

[apecloud-bot]

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[codecov]

Codecov Report

❌ Patch coverage is 61.53846% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.78%. Comparing base (5a57a85) to head (86ad07d).

Files with missing lines	Patch %	Lines
pkg/dataprotection/restore/manager.go	53.84%	4 Missing and 2 partials ⚠️
pkg/dataprotection/restore/builder.go	69.23%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10616      +/-   ##
==========================================
+ Coverage   63.75%   63.78%   +0.02%     
==========================================
  Files         520      520              
  Lines       62957    62965       +8     
==========================================
+ Hits        40138    40160      +22     
+ Misses      19201    19195       -6     
+ Partials     3618     3610       -8     

Flag	Coverage Δ
unittests	63.78% <61.53%> (+0.02%)	⬆️

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