[AZ-1126] Migrate capturedAt to DateTimeOffset

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/03_implementation/batch_01_cycle13_report.md

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+# Batch Report
+
+**Batch**: 1
+**Tasks**: AZ-1126_captured_at_datetimeoffset
+**Date**: 2026-06-26
+**Cycle**: 13
+
+## Task Results
+
+| Task | Status | Files Modified | Tests | AC Coverage | Issues |
+|------|--------|---------------|-------|-------------|--------|
+| AZ-1126 | Done | 12 files | pass | 4/4 ACs covered | None |
+
+## AC Test Coverage: All covered
+
+| AC | Evidence |
+|----|----------|
+| AC-1 | `UavTileMetadataValidatorTests`, `UavTileQualityGateTests`, `UavTileUploadHandlerTests` |
+| AC-2 | `UtcOffsetRequiredDateTimeOffsetConverterTests`, `UavUploadValidationTests.ItemCapturedAtOffsetLess_Returns400` |
+| AC-3 | `UavUploadValidationTests.HappyPath_Returns200`, existing `UavUploadTests` suite |
+| AC-4 | `uav-tile-upload.md` v1.2.1 change log |
+
+## Code Review Verdict: PASS_WITH_WARNINGS
+
+Self-review: type migration is localized; filter now surfaces `JsonException.Message` for metadata parse failures (improves flightId and capturedAt diagnostics). No architecture drift.
+
+## Auto-Fix Attempts: 1
+
+Integration test initially failed because `UavUploadValidationFilter` replaced all `JsonException` messages with a generic parse error; fixed by propagating the converter message.
+
+## Stuck Agents: None
+
+## Full Test Run
+
+`./scripts/run-tests.sh` (mode=full) — all unit + integration tests passed after filter fix.
+
+## Next Batch: All tasks complete