Add transport DDL, repos and transport service

Add database DDL and server-side data access/service layers for transport domain. New SQL DDL files create transport_types, lines, stations, platforms and platform_lines tables (with FKs, indexes, spatial POINT column, CHECK constraints, and triggers to populate location). New repositories implement queries and CRUD for lines, stations, platforms and platform_lines (including distance/nearest-platform and accessibility queries). A transportService aggregates repo functions and exposes high-level operations (CRUD, station/line lookups, platform-line management and nearest-platform validation).

data/ddl/08_lines.sql

@@ -0,0 +1,17 @@
+CREATE TABLE IF NOT EXISTS `lines` (
+    `id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    `code` VARCHAR(50) NOT NULL UNIQUE,
+    `name` VARCHAR(255),
+    `textColorHex` VARCHAR(7),
+    `backColorHex` VARCHAR(7),
+    `transportTypeId` INT UNSIGNED NOT NULL,
+    `createdAt` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    PRIMARY KEY (`id`),
+
+    CONSTRAINT `fk_lines_transport_type`
+        FOREIGN KEY (`transportTypeId`)
+        REFERENCES `transport_types` (`id`),
+
+    INDEX `idx_transport_type` (`transportTypeId`)
+);