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-tauri/src/models/ai.rs

@@ -57,3 +57,137 @@ pub struct OllamaTagsResponse {
 pub struct OllamaModel {
     pub name: String,
 }
+
+// --- Wave 1: Validation ---
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum ValidationStatus {
+    Pending,
+    Generating,
+    Running,
+    Passed,
+    Failed,
+    Error,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidationRule {
+    pub id: String,
+    pub description: String,
+    pub generated_sql: String,
+    pub status: ValidationStatus,
+    pub violation_count: u64,
+    pub sample_violations: Vec<Vec<serde_json::Value>>,
+    pub violation_columns: Vec<String>,
+    pub error: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ValidationReport {
+    pub rules: Vec<ValidationRule>,
+    pub total_rules: usize,
+    pub passed: usize,
+    pub failed: usize,
+    pub errors: usize,
+    pub execution_time_ms: u128,
+}
+
+// --- Wave 2: Data Generator ---
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct GenerateDataParams {
+    pub connection_id: String,
+    pub schema: String,
+    pub table: String,
+    pub row_count: u32,
+    pub include_related: bool,
+    pub custom_instructions: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct GeneratedDataPreview {
+    pub tables: Vec<GeneratedTableData>,
+    pub insert_order: Vec<String>,
+    pub total_rows: u32,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct GeneratedTableData {
+    pub schema: String,
+    pub table: String,
+    pub columns: Vec<String>,
+    pub rows: Vec<Vec<serde_json::Value>>,
+    pub row_count: u32,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DataGenProgress {
+    pub gen_id: String,
+    pub stage: String,
+    pub percent: u8,
+    pub message: String,
+    pub detail: Option<String>,
+}
+
+// --- Wave 3A: Index Advisor ---
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TableStats {
+    pub schema: String,
+    pub table: String,
+    pub seq_scan: i64,
+    pub idx_scan: i64,
+    pub n_live_tup: i64,
+    pub table_size: String,
+    pub index_size: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct IndexStats {
+    pub schema: String,
+    pub table: String,
+    pub index_name: String,
+    pub idx_scan: i64,
+    pub index_size: String,
+    pub definition: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct SlowQuery {
+    pub query: String,
+    pub calls: i64,
+    pub total_time_ms: f64,
+    pub mean_time_ms: f64,
+    pub rows: i64,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum IndexRecommendationType {
+    CreateIndex,
+    DropIndex,
+    ReplaceIndex,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct IndexRecommendation {
+    pub id: String,
+    pub recommendation_type: IndexRecommendationType,
+    pub table_schema: String,
+    pub table_name: String,
+    pub index_name: Option<String>,
+    pub ddl: String,
+    pub rationale: String,
+    pub estimated_impact: String,
+    pub priority: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct IndexAdvisorReport {
+    pub table_stats: Vec<TableStats>,
+    pub index_stats: Vec<IndexStats>,
+    pub slow_queries: Vec<SlowQuery>,
+    pub recommendations: Vec<IndexRecommendation>,
+    pub has_pg_stat_statements: bool,
+}