Add Re-sync button for SimpleFIN connections

Resets LastSyncAt on all linked accounts so the next sync
re-fetches the full 90-day transaction window. Duplicate
detection prevents re-importing existing transactions.

- POST /api/bank-sync/connections/{id}/reset-sync endpoint
- Re-sync button shown only on SimpleFIN connection cards

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

frontend/src/views/settings/SettingsView.vue

@@ -184,6 +184,16 @@
               >
                 Sync Now
               </v-btn>
+              <v-btn
+                v-if="conn.provider === 'SimpleFIN'"
+                variant="tonal"
+                color="secondary"
+                prepend-icon="mdi-refresh"
+                :loading="resyncingConnections[conn.id]"
+                @click="resyncFromScratch(conn)"
+              >
+                Re-sync
+              </v-btn>
               <v-btn
                 variant="tonal"
                 :color="conn.isActive ? 'warning' : 'success'"
@@ -530,6 +540,7 @@ const connections = ref<SyncConnection[]>([])
 const accounts = ref<Account[]>([])
 const syncIntervals = reactive<Record<string, number>>({})
 const syncingConnections = reactive<Record<string, boolean>>({})
+const resyncingConnections = reactive<Record<string, boolean>>({})
 
 // Plaid credentials
 const plaidCredentials = ref<PlaidCredentials>({ isConfigured: false, environment: 'sandbox' })
@@ -814,6 +825,20 @@ async function syncNow(conn: SyncConnection) {
   }
 }
 
+async function resyncFromScratch(conn: SyncConnection) {
+  resyncingConnections[conn.id] = true
+  try {
+    await bankSyncApi.resetSync(conn.id)
+    await bankSyncApi.syncNow(conn.id)
+    syncingConnections[conn.id] = true
+  } catch (err: any) {
+    errorMessage.value = err.response?.data?.error || 'Re-sync failed'
+    showError.value = true
+  } finally {
+    resyncingConnections[conn.id] = false
+  }
+}
+
 // Handle sync results via SignalR notification
 const { notifications } = useNotifications()
 watch(notifications, (notifs) => {