Add import/export and backup system (Milestone 8)

- Obsidian vault importer with wikilink → edge conversion
- Markdown folder importer with frontmatter parsing
- Markdown exporter with wikilinks and frontmatter
- JSON-LD linked data exporter
- Database backup/restore functionality
- CLI: import, backup, restore-backup, list-backups
- MCP tools: memory_import, memory_backup, memory_export_markdown, memory_export_jsonld

src/cli/commands/import.ts

@@ -0,0 +1,66 @@
+import { Command } from 'commander';
+import chalk from 'chalk';
+import { importObsidian } from '../../core/import/obsidian';
+import { importMarkdown } from '../../core/import/markdown';
+
+export const importCommand = new Command('import')
+  .description('Import data from external sources')
+  .argument('<source>', 'Source type: obsidian, markdown')
+  .argument('<path>', 'Path to import from')
+  .option('-t, --tags <tags>', 'Additional tags (comma-separated)')
+  .option('-k, --kind <kind>', 'Node kind (default: memory)')
+  .option('--hierarchy', 'Create folder hierarchy (obsidian only)')
+  .option('--dry-run', 'Preview import without making changes')
+  .action(async (source: string, inputPath: string, opts) => {
+    try {
+      const tags = opts.tags?.split(',').map((t: string) => t.trim());
+
+      switch (source.toLowerCase()) {
+        case 'obsidian': {
+          console.log(chalk.cyan(`Importing Obsidian vault from ${inputPath}...`));
+          const result = await importObsidian(inputPath, {
+            kind: opts.kind,
+            hierarchy: opts.hierarchy,
+            dryRun: opts.dryRun,
+          });
+
+          if (opts.dryRun) {
+            console.log(chalk.yellow(`Dry run: would import ${result.imported} notes`));
+            console.log(chalk.dim(`  Would create ${result.edges} edges from wikilinks`));
+          } else {
+            console.log(chalk.green(`✓ Imported ${result.imported} notes`));
+            if (result.edges > 0) {
+              console.log(chalk.dim(`  Created ${result.edges} edges from wikilinks`));
+            }
+            if (result.skipped > 0) {
+              console.log(chalk.yellow(`  Skipped ${result.skipped} files (already exist)`));
+            }
+          }
+          break;
+        }
+        case 'markdown':
+        case 'md': {
+          console.log(chalk.cyan(`Importing markdown files from ${inputPath}...`));
+          const result = await importMarkdown(inputPath, {
+            kind: opts.kind as any,
+            tags,
+            dryRun: opts.dryRun,
+          });
+
+          if (opts.dryRun) {
+            console.log(chalk.yellow(`Dry run: would import ${result.imported} files`));
+          } else {
+            console.log(chalk.green(`✓ Imported ${result.imported} files`));
+          }
+          break;
+        }
+        default:
+          console.error(chalk.red(`Unknown source type: ${source}`));
+          console.log(chalk.dim('Supported: obsidian, markdown'));
+          process.exit(1);
+      }
+    } catch (err: any) {
+      console.error(chalk.red(`Error: ${err.message}`));
+      process.exit(1);
+    }
+  });