feat(ui): improve client form modal UX

- Rename tabs: "Basic" → "Basics", "Config" → "Credentials"
- Move reverseTag field from Credentials tab to Basics tab
- Move IP log button inline with limitIp field (tooltip button, edit mode only)
- Hide random email button when editing an existing client
- Add tooltips to totalGB and limitIp fields with descriptive hints
- Rename labels: "Total Sent/Received (GB)" → "Traffic Limit (GB)", "Duration" → "Duration (days)"
- Add renewDays translation key for auto-renew label with unit hint
- Remove redundant filterOption and width style from AutoComplete group selectors
- Update all 15 locale files with new and renamed translation keys

frontend/src/pages/clients/ClientBulkAddModal.tsx

@@ -288,11 +288,7 @@ export default function ClientBulkAddModal({
               placeholder={t('pages.clients.groupPlaceholder')}
               options={groups.map((g) => ({ value: g }))}
               onChange={(v) => update('group', v ?? '')}
-              filterOption={(input, option) =>
-                String(option?.value ?? '').toLowerCase().includes((input || '').toLowerCase())
-              }
               allowClear
-              style={{ width: '100%' }}
             />
           </Form.Item>