feat(filing): scaffold Task #3 Feature 1 — file mail to Case/Contact

Core layer:
- FilingService: orchestrates batch filing with 401-aborts-batch, 409-treats-as-success, transient errors fall to DiskRetryQueue
- DiskRetryQueue: atomic write (tmp + rename), Hebrew UTF-8 round-trip, idempotent remove
- Models: MailEnvelope (STA-extracted primitives), FilingTarget, FilingOutcome enum, FilingItemResult, FilingBatchSummary, RetryQueueItem
- EspoCrmClient.CreateContactAsync for "create contact from sender" flow

UI layer:
- FileToCaseDialog (WPF, RTL, Hebrew labels) with grouped search results + recent sidebar
- FileToCaseViewModel: 250ms debounced GlobalSearch, create-contact-from-sender command, DialogResult signaling

Tests (38 passing):
- FilingServiceTests: happy path, 409, 401 aborts batch, transient enqueues, queue failure → Failed, target propagation, null guards
- DiskRetryQueueTests: id assignment, Hebrew round-trip, corrupt-file skip, idempotent remove, atomic overwrite

VSTO host project (OutlookAddin.csproj) regenerated; ThisAddIn wiring in follow-up commits.
gitignore: exclude .claude/settings.local.json (per-machine).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -44,6 +44,9 @@ appsettings.local.json
 *.log
 logs/
 
+# Claude Code local settings (per-machine)
+.claude/settings.local.json
+
 # OS
 .DS_Store
 Thumbs.db