refactor(scheduling): shared types, structured reason, cross-region candidates

- Extract shared types to src/shared/scheduling/types.ts (client/server both re-export)
- Convert SchedulingSuggestion.reason from string to structured { lines, conclusion }
- Remove hard region filter; algorithm keeps cross-region candidates with isSameRegion flag
- SuggestionDetail renders same-region vs cross-region sections with a divider
- Close detail modal when selected suggestion no longer exists in data
- Unify estimatedGain definition (strict canQualifyAfterSwap) between algorithm and API layers

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/modules/scheduling/SchedulingModule.tsx

@@ -161,6 +161,13 @@ export default function SchedulingModule() {
   useEffect(() => { loadData(); }, [loadData]);
   const handleNotifySuccess = useCallback(() => { loadData(); }, [loadData]);
 
+  // Close detail modal if selected suggestion is filtered out or no longer exists
+  useEffect(() => {
+    if (!selectedSuggestion || !data) return;
+    const stillExists = data.suggestions.some(s => s.id === selectedSuggestion.id);
+    if (!stillExists) setSelectedSuggestion(null);
+  }, [data, selectedSuggestion]);
+
   const filterOptions = useMemo(() => {
     if (!data) return { regions: [], vehicleTypes: [], customers: [], departments: [], managers: [] };
     const r = new Set<string>(), t = new Set<string>(), c = new Set<string>(), d = new Set<string>(), m = new Set<string>();