fix(postgresql): filter PITR restore archive objects

[weicao]

What

Skip compressed repository objects unless their basename is a PostgreSQL WAL segment or timeline-history archive before PITR pull and inspection.

Why

The restore traversal accepted every name containing .zst. An unrelated object ordered between the local start WAL and the next valid segment could be pulled, inspected, mistaken for the target boundary, and cause the real WAL to be skipped while preparation returned success.

Tests

• RED (62e5df853): Bash 3.2 focused ShellSpec, 16 examples / 1 failure / 2 failed assertions
• GREEN: Bash 3.2 focused ShellSpec, 16 examples / 0 failures
• GREEN: Bash 5.3 full PostgreSQL ShellSpec, 284 examples / 0 failures
• ShellCheck error severity, Bash syntax, and git diff --check
• helm lint addons/postgresql: 1 chart / 0 failures
• helm template: 41 documents / 1,014,308 bytes

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (9fd582d) to head (8b549e1).

Files with missing lines	Patch %	Lines
...ns/postgresql/scripts-ut-spec/pitr_restore_spec.sh	0.00%	8 Missing ⚠️

Additional details and impacted files

@@                              Coverage Diff                              @@
##           easton/pg-pitr-restore-recovery-time-failfast   #3401   +/-   ##
=============================================================================
  Coverage                                           0.00%   0.00%           
=============================================================================
  Files                                                195     195           
  Lines                                              28372   28380    +8     
=============================================================================
- Misses                                             28372   28380    +8     

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