feat: add AI data validation, test data generator, index advisor, and snapshots

Four new killer features leveraging AI (Ollama) and PostgreSQL internals:

- Data Validation: describe quality rules in natural language, AI generates
  SQL to find violations, run with pass/fail results and sample violations
- Test Data Generator: right-click table to generate realistic FK-aware test
  data with AI, preview before inserting in a transaction
- Index Advisor: analyze pg_stat tables + AI recommendations for CREATE/DROP
  INDEX with one-click apply
- Data Snapshots: export selected tables to JSON (FK-ordered), restore from
  file with optional truncate in a transaction

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

src/hooks/use-data-generator.ts

@@ -0,0 +1,73 @@
+import { useState, useEffect, useCallback, useRef } from "react";
+import { useMutation } from "@tanstack/react-query";
+import {
+  generateTestDataPreview,
+  insertGeneratedData,
+  onDataGenProgress,
+} from "@/lib/tauri";
+import type { GenerateDataParams, DataGenProgress, GeneratedDataPreview } from "@/types";
+
+export function useDataGenerator() {
+  const [progress, setProgress] = useState<DataGenProgress | null>(null);
+  const genIdRef = useRef<string>("");
+
+  const previewMutation = useMutation({
+    mutationFn: ({
+      params,
+      genId,
+    }: {
+      params: GenerateDataParams;
+      genId: string;
+    }) => {
+      genIdRef.current = genId;
+      setProgress(null);
+      return generateTestDataPreview(params, genId);
+    },
+  });
+
+  const insertMutation = useMutation({
+    mutationFn: ({
+      connectionId,
+      preview,
+    }: {
+      connectionId: string;
+      preview: GeneratedDataPreview;
+    }) => insertGeneratedData(connectionId, preview),
+  });
+
+  useEffect(() => {
+    const unlistenPromise = onDataGenProgress((p) => {
+      if (p.gen_id === genIdRef.current) {
+        setProgress(p);
+      }
+    });
+    return () => {
+      unlistenPromise.then((unlisten) => unlisten());
+    };
+  }, []);
+
+  const previewRef = useRef(previewMutation);
+  previewRef.current = previewMutation;
+  const insertRef = useRef(insertMutation);
+  insertRef.current = insertMutation;
+
+  const reset = useCallback(() => {
+    previewRef.current.reset();
+    insertRef.current.reset();
+    setProgress(null);
+    genIdRef.current = "";
+  }, []);
+
+  return {
+    generatePreview: previewMutation.mutate,
+    preview: previewMutation.data as GeneratedDataPreview | undefined,
+    isGenerating: previewMutation.isPending,
+    generateError: previewMutation.error ? String(previewMutation.error) : null,
+    insertData: insertMutation.mutate,
+    insertedRows: insertMutation.data as number | undefined,
+    isInserting: insertMutation.isPending,
+    insertError: insertMutation.error ? String(insertMutation.error) : null,
+    progress,
+    reset,
+  };
+}