Fix server-side pagination returning same data on every page

v-data-table-server re-emits update:options when items/totalCount
change, creating a loop that resets to page 1. Guard against
redundant fetches by skipping when page and pageSize haven't
changed. Remove duplicate loadTransactions from onMounted since
the table's initial update:options event handles the first load.

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

frontend/src/views/transactions/TransactionsView.vue

@@ -263,10 +263,12 @@ onMounted(async () => {
     const acct = accountsStore.accounts.find(a => a.id === props.id)
     accountName.value = acct?.name || ''
   }
-  await loadTransactions()
 })
 
-watch(() => props.id, () => loadTransactions())
+watch(() => props.id, () => {
+  page.value = 1
+  loadTransactions()
+})
 
 async function loadCategories() {
   try {
@@ -305,7 +307,10 @@ function doSearch() {
   loadTransactions()
 }
 
+let initialized = false
 function onTableOptions(options: { page: number; itemsPerPage: number }) {
+  if (initialized && options.page === page.value && options.itemsPerPage === itemsPerPage.value) return
+  initialized = true
   page.value = options.page
   itemsPerPage.value = options.itemsPerPage
   loadTransactions()