Fix 7 data mutation layer risks identified in audit

- save()/saveAndRunDataListeners() now return @discardableResult Bool;
  listeners only fire on successful save
- MoodLogger.updateMood() now recalculates streak, updates Live Activity,
  and notifies watch (was missing these side effects)
- CSV import uses new addBatch()/importMoods() for O(1) side effects
  instead of O(n) per-row widget reloads and streak calcs
- Foreground task ordering: fillInMissingDates() now runs before
  removeDuplicates() so backfill-created duplicates are caught same cycle
- WidgetMoodSaver deletes ALL entries for date (was fetchLimit=1, leaving
  CloudKit sync duplicates behind)
- cleanupPhotoIfNeeded logs warning on failed photo deletion instead of
  silently orphaning files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Shared/Persisence/DataController.swift

@@ -52,19 +52,32 @@ final class DataController: ObservableObject {
         editedDataClosure.append(closure)
     }
 
-    func saveAndRunDataListeners() {
-        save()
-        for closure in editedDataClosure {
-            closure()
+    @discardableResult
+    func saveAndRunDataListeners() -> Bool {
+        let success = save()
+        if success {
+            for closure in editedDataClosure {
+                closure()
+            }
         }
+        return success
     }
 
-    func save() {
-        guard modelContext.hasChanges else { return }
+    @discardableResult
+    func save() -> Bool {
+        guard modelContext.hasChanges else { return true }
         do {
             try modelContext.save()
+            return true
         } catch {
-            Self.logger.error("Failed to save context: \(error.localizedDescription)")
+            Self.logger.error("Failed to save context, retrying: \(error.localizedDescription)")
+            do {
+                try modelContext.save()
+                return true
+            } catch {
+                Self.logger.critical("Failed to save context after retry: \(error.localizedDescription)")
+                return false
+            }
         }
     }