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-validation.ts

@@ -0,0 +1,38 @@
+import { useMutation } from "@tanstack/react-query";
+import {
+  generateValidationSql,
+  runValidationRule,
+  suggestValidationRules,
+} from "@/lib/tauri";
+
+export function useGenerateValidationSql() {
+  return useMutation({
+    mutationFn: ({
+      connectionId,
+      ruleDescription,
+    }: {
+      connectionId: string;
+      ruleDescription: string;
+    }) => generateValidationSql(connectionId, ruleDescription),
+  });
+}
+
+export function useRunValidationRule() {
+  return useMutation({
+    mutationFn: ({
+      connectionId,
+      sql,
+      sampleLimit,
+    }: {
+      connectionId: string;
+      sql: string;
+      sampleLimit?: number;
+    }) => runValidationRule(connectionId, sql, sampleLimit),
+  });
+}
+
+export function useSuggestValidationRules() {
+  return useMutation({
+    mutationFn: (connectionId: string) => suggestValidationRules(connectionId),
+  });
+}