feat(ui): wire admin add-account endpoint into Chart of Accounts

Surface the existing POST /api/v1/admin/accounts endpoint in the UI: a
super-user-only 'Add Account' button on the Chart of Accounts card opens
a dialog for the hierarchical account name + optional description, posts
with the wallet admin key (require_super_user), then reloads accounts.
Client-side prefix validation mirrors the server's _VALID_ACCOUNT_PREFIXES.
No currency input — an Open directive does not require currency constraints.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

static/js/index.js

@@ -69,6 +69,12 @@ window.app = Vue.createApp({
         userWalletId: '',
         loading: false
       },
+      addAccountDialog: {
+        show: false,
+        name: '',
+        description: '',
+        loading: false
+      },
       receivableDialog: {
         show: false,
         selectedUser: '',
@@ -566,6 +572,45 @@ window.app = Vue.createApp({
         this.syncingAccounts = false
       }
     },
+    showAddAccountDialog() {
+      this.addAccountDialog.name = ''
+      this.addAccountDialog.description = ''
+      this.addAccountDialog.show = true
+    },
+    async submitAddAccount() {
+      const name = (this.addAccountDialog.name || '').trim()
+      const validPrefixes = ['Assets:', 'Liabilities:', 'Equity:', 'Income:', 'Expenses:']
+      if (!validPrefixes.some(p => name.startsWith(p))) {
+        this.$q.notify({
+          type: 'warning',
+          message: `Account name must start with one of: ${validPrefixes.join(', ')}`
+        })
+        return
+      }
+      this.addAccountDialog.loading = true
+      try {
+        const {data} = await LNbits.api.request(
+          'POST',
+          '/libra/api/v1/admin/accounts',
+          this.g.user.wallets[0].adminkey,
+          {
+            name,
+            description: this.addAccountDialog.description || null
+          }
+        )
+        this.$q.notify({
+          type: 'positive',
+          message: `Account ${data.account_name} created` +
+            (data.synced_to_libra_db ? '' : ' (sync pending)')
+        })
+        this.addAccountDialog.show = false
+        await this.loadAccounts()
+      } catch (error) {
+        LNbits.utils.notifyApiError(error)
+      } finally {
+        this.addAccountDialog.loading = false
+      }
+    },
     showSettingsDialog() {
       this.settingsDialog.libraWalletId = this.settings?.libra_wallet_id || ''
       this.settingsDialog.favaUrl = this.settings?.fava_url || 'http://localhost:3333'