feat: add index type, included columns, filter, and comment support

- Add filter, index_type, included_columns, and comment fields to IndexInfo
- PostgreSQL: query pg_am for index type, use indnkeyatts to split key/included columns, retrieve index comments via obj_description()
- SQL Server: add type_desc, filter_definition, included columns via is_included_column
- MySQL: add INDEX_TYPE from information_schema.STATISTICS
- Oracle: add INDEX_TYPE from ALL_INDEXES
- DDL generation: add USING (PostgreSQL), type prefix + INCLUDE + WHERE (SQL Server), COMMENT ON INDEX (PostgreSQL)
- Frontend: update types, state mapping, SQL generation, and i18n translations

src/types/database.ts

@@ -44,6 +44,7 @@ export interface ColumnInfo {
   comment?: string | null;
   numeric_precision?: number | null;
   numeric_scale?: number | null;
+  character_maximum_length?: number | null;
 }
 
 export interface IndexInfo {
@@ -51,6 +52,10 @@ export interface IndexInfo {
   columns: string[];
   is_unique: boolean;
   is_primary: boolean;
+  filter?: string | null;
+  index_type?: string | null;
+  included_columns?: string[] | null;
+  comment?: string | null;
 }
 
 export interface ForeignKeyInfo {