Backlog item 3 (Wave 2), GmailController slice. Pure mechanical extraction,
no behaviour change:
- GmailDtos.cs: the 26 inline record DTOs, moved to a partial-class file so
every existing GmailController.XyzDto reference (tests included) keeps
working unchanged.
- GmailParsing.cs: the 8 pure static helpers (ApplySyncBoundary,
LooksLikeJobRelatedThread, ToConfidence, ExtractFirstEmail/RecruiterName/
CompanyName/RoleFromSubject, BuildPopupHtml), same partial-class approach.
GmailController.cs: 1200 -> 1022 lines. 169/169 green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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