fix(ops): fail fast on missing backup method

[leon-ape]

Fixes #10816.

Release 1.1 counterpart of #10818.

Problem

A Backup may report status.phase: Completed while status.backupMethod is empty. The restore plan detects that invalid state, but the scale-out OpsRequest keeps retrying because the error is not terminal.

Changes

• keep detection of the incomplete Backup status in the shared restore plan
• classify its RestoreFailed result as fatal at the scale-out Operations boundary
• verify the invalid completed Backup is terminal and creates no Restore

Scope

This PR only changes missing-backupMethod error classification on release-1.1. It does not change restore environment, namespaces, authorization, VolumeSnapshot behavior, no-target-volume handling, or source-target selection.

Validation

• scripts/codex-go-test.sh ./pkg/operations -count=1
• git diff --check

[apecloud-bot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.50%. Comparing base (316faf0) to head (88a463e).

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.1   #10822      +/-   ##
===============================================
- Coverage        55.52%   55.50%   -0.02%     
===============================================
  Files              550      550              
  Lines            62326    62328       +2     
===============================================
- Hits             34604    34595       -9     
- Misses           24407    24413       +6     
- Partials          3315     3320       +5     

Flag	Coverage Δ
unittests	55.50% <100.00%> (-0.02%)	⬇️

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[leon-ape]

/approve