Fix SQLite analyzer permission error flags

[sjh9714]

Summary

Fixes #591.

When the SQLite analyzer scanned a readable directory that contained an unreadable descendant, the descendant kept its ! flag but the parent directory row kept its original blank flag. This made non-interactive --db output miss the . warning prefix for parent directories whose totals may be incomplete.

Changes

• Persist directory flags when final SQLite analyzer stats are written.
• Propagate child !/. flags to the finalized parent directory flag.
• Add a regression test for a nested chmod-000 directory scanned through the SQLite analyzer.

Testing

• go test ./pkg/analyze -run TestSqliteAnalyzerPropagatesChildPermissionError -count=1 (failed before the fix, passed after)
• go test -v -covermode=count ./...
• go build -o /tmp/gdu-pr-591-fixed ./cmd/gdu
• go vet ./...
• Manual CLI check with a nested unreadable directory: gdu --no-progress --no-color --no-prefix --non-interactive --db <tmp>/gdu.sqlite <tmp>/myfolder

Note: I used Codex while preparing this change, and I reviewed the final diff and ran the listed checks locally.

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.49%. Comparing base (da4d262) to head (55697a2).

Files with missing lines	Patch %	Lines
pkg/analyze/sqlite.go	91.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #598      +/-   ##
==========================================
+ Coverage   85.45%   85.49%   +0.04%     
==========================================
  Files          55       55              
  Lines        6173     6177       +4     
==========================================
+ Hits         5275     5281       +6     
+ Misses        691      690       -1     
+ Partials      207      206       -1     

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