feat: implement database management service layer and frontend SQL import/export utility

frontend/src/components/TransferContent.tsx

@@ -38,22 +38,23 @@ const TransferContent: React.FC<TransferContentProps> = ({ mode = 'both' }) => {
   const [error, setError] = useState<string | null>(null);
   const [file, setFile] = useState<File | null>(null);
 
-  const handleExport = async () => {
+  const handleExport = async (onlyStructure: boolean = false) => {
     setLoading(true);
     setError(null);
     setSuccess(null);
     try {
-      const response = await SchemaService.exportDatabase(activeDatabase || undefined, activeTable || undefined);
+      const response = await SchemaService.exportDatabase(activeDatabase || undefined, activeTable || undefined, undefined, onlyStructure);
       const url = window.URL.createObjectURL(new Blob([response.data]));
       const link = document.createElement('a');
       link.href = url;
+      const suffix = onlyStructure ? '-schema' : '';
       const filename = activeTable 
-        ? `${activeTable}-${new Date().toISOString().split('T')[0]}.sql` 
-        : `backup-${activeDatabase || 'all'}-${new Date().toISOString().split('T')[0]}.sql`;
+        ? `${activeTable}${suffix}-${new Date().toISOString().split('T')[0]}.sql` 
+        : `backup-${activeDatabase || 'all'}${suffix}-${new Date().toISOString().split('T')[0]}.sql`;
       link.setAttribute('download', filename);
       document.body.appendChild(link);
       link.click();
-      setSuccess(`${activeTable ? 'Table' : 'Database'} exported successfully!`);
+      setSuccess(`${activeTable ? 'Table' : 'Database'} ${onlyStructure ? 'structure' : ''} exported successfully!`);
     } catch (err: any) {
       setError('Export failed: ' + (err.response?.data?.error || err.message));
     } finally {
@@ -138,22 +139,35 @@ const TransferContent: React.FC<TransferContentProps> = ({ mode = 'both' }) => {
                   <TableCell sx={{ py: 3 }}>
                     <Typography variant="h6" sx={{ fontWeight: 700, mb: 0.5 }}>Export {activeTable ? 'Table' : 'Database'}</Typography>
                     <Typography variant="body2" color="text.secondary">
-                      Create a full backup of the current {activeTable ? 'table' : 'database'}: <br/>
+                      Create a backup of the current {activeTable ? 'table' : 'database'}: <br/>
                       <Box component="span" sx={{ color: 'primary.main', fontWeight: 600 }}>
                         {activeTable ? `${activeDatabase}.${activeTable}` : (activeDatabase || 'All Databases')}
                       </Box>
                     </Typography>
                   </TableCell>
                   <TableCell align="right" sx={{ py: 3 }}>
-                    <Button 
-                      variant="contained" 
-                      startIcon={<CloudDownload />}
-                      onClick={handleExport}
-                      disabled={loading}
-                      sx={{ borderRadius: 2, px: 3, py: 1, fontWeight: 700, minWidth: 160 }}
-                    >
-                      Start Export
-                    </Button>
+                    <Stack direction="row" spacing={1} justifyContent="flex-end">
+                      <Button 
+                        variant="outlined" 
+                        color="primary"
+                        startIcon={<CloudDownload />}
+                        onClick={() => handleExport(true)}
+                        disabled={loading}
+                        sx={{ borderRadius: 2, px: 2, py: 1, fontWeight: 700 }}
+                      >
+                        Export Structure
+                      </Button>
+                      <Button 
+                        variant="contained" 
+                        color="primary"
+                        startIcon={<CloudDownload />}
+                        onClick={() => handleExport(false)}
+                        disabled={loading}
+                        sx={{ borderRadius: 2, px: 2, py: 1, fontWeight: 700 }}
+                      >
+                        Full Export
+                      </Button>
+                    </Stack>
                   </TableCell>
                 </TableRow>
               )}

frontend/src/services/api.ts

@@ -39,10 +39,11 @@ export const SchemaService = {
   bulkAction: (data: { tables: string[], action: string, database: string }) => api.post('/schema/bulk-action', data),
   batchUpdate: (table: string, changes: any[]) => api.post(`/schema/${table}/batch-update`, { changes }),
   executeQuery: (query: string) => api.post('/schema/execute', { query }),
-  exportDatabase: (database?: string, table?: string, filters?: any) => api.post('/schema/export', { 
+  exportDatabase: (database?: string, table?: string, filters?: any, structureOnly: boolean = false) => api.post('/schema/export', { 
     database, 
     table, 
-    filters: filters ? JSON.stringify(filters) : undefined 
+    filters: filters ? JSON.stringify(filters) : undefined,
+    structureOnly
   }, { responseType: 'blob' }),
   importDatabase: (formData: FormData) => api.post('/schema/import', formData, {
     headers: { 'Content-Type': 'multipart/form-data' }