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-snapshots.ts

@@ -0,0 +1,131 @@
+import { useState, useEffect, useCallback, useRef } from "react";
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
+import {
+  createSnapshot,
+  restoreSnapshot,
+  listSnapshots,
+  readSnapshotMetadata,
+  onSnapshotProgress,
+} from "@/lib/tauri";
+import type {
+  CreateSnapshotParams,
+  RestoreSnapshotParams,
+  SnapshotProgress,
+  SnapshotMetadata,
+} from "@/types";
+
+export function useListSnapshots() {
+  return useQuery({
+    queryKey: ["snapshots"],
+    queryFn: listSnapshots,
+    staleTime: 30_000,
+  });
+}
+
+export function useReadSnapshotMetadata() {
+  return useMutation({
+    mutationFn: (filePath: string) => readSnapshotMetadata(filePath),
+  });
+}
+
+export function useCreateSnapshot() {
+  const [progress, setProgress] = useState<SnapshotProgress | null>(null);
+  const snapshotIdRef = useRef<string>("");
+  const queryClient = useQueryClient();
+
+  const mutation = useMutation({
+    mutationFn: ({
+      params,
+      snapshotId,
+      filePath,
+    }: {
+      params: CreateSnapshotParams;
+      snapshotId: string;
+      filePath: string;
+    }) => {
+      snapshotIdRef.current = snapshotId;
+      setProgress(null);
+      return createSnapshot(params, snapshotId, filePath);
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["snapshots"] });
+    },
+  });
+
+  useEffect(() => {
+    const unlistenPromise = onSnapshotProgress((p) => {
+      if (p.snapshot_id === snapshotIdRef.current) {
+        setProgress(p);
+      }
+    });
+    return () => {
+      unlistenPromise.then((unlisten) => unlisten());
+    };
+  }, []);
+
+  const mutationRef = useRef(mutation);
+  mutationRef.current = mutation;
+
+  const reset = useCallback(() => {
+    mutationRef.current.reset();
+    setProgress(null);
+    snapshotIdRef.current = "";
+  }, []);
+
+  return {
+    create: mutation.mutate,
+    result: mutation.data as SnapshotMetadata | undefined,
+    error: mutation.error ? String(mutation.error) : null,
+    isCreating: mutation.isPending,
+    progress,
+    reset,
+  };
+}
+
+export function useRestoreSnapshot() {
+  const [progress, setProgress] = useState<SnapshotProgress | null>(null);
+  const snapshotIdRef = useRef<string>("");
+
+  const mutation = useMutation({
+    mutationFn: ({
+      params,
+      snapshotId,
+    }: {
+      params: RestoreSnapshotParams;
+      snapshotId: string;
+    }) => {
+      snapshotIdRef.current = snapshotId;
+      setProgress(null);
+      return restoreSnapshot(params, snapshotId);
+    },
+  });
+
+  useEffect(() => {
+    const unlistenPromise = onSnapshotProgress((p) => {
+      if (p.snapshot_id === snapshotIdRef.current) {
+        setProgress(p);
+      }
+    });
+    return () => {
+      unlistenPromise.then((unlisten) => unlisten());
+    };
+  }, []);
+
+  const mutationRef = useRef(mutation);
+  mutationRef.current = mutation;
+
+  const reset = useCallback(() => {
+    mutationRef.current.reset();
+    setProgress(null);
+    snapshotIdRef.current = "";
+  }, []);
+
+  return {
+    restore: mutation.mutate,
+    rowsRestored: mutation.data as number | undefined,
+    error: mutation.error ? String(mutation.error) : null,
+    isRestoring: mutation.isPending,
+    progress,
+    reset,
+  };
+}