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/11_platform_lines.sql

@@ -0,0 +1,17 @@
+CREATE TABLE IF NOT EXISTS `platform_lines` (
+    `id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    `platformId` INT UNSIGNED NOT NULL,
+    `lineId` INT UNSIGNED NOT NULL,
+    `directionId` TINYINT UNSIGNED NOT NULL DEFAULT 0,
+    `orderInLine` SMALLINT UNSIGNED NOT NULL,
+
+    PRIMARY KEY (id),
+    UNIQUE KEY uq_platform_line_dir (platformId, lineId, directionId),
+    UNIQUE KEY uq_line_dir_order (lineId, directionId, orderInLine),
+    INDEX idx_pl_line (lineId),
+
+    CONSTRAINT fk_pl_platform FOREIGN KEY (platformId)
+        REFERENCES platforms(id) ON DELETE CASCADE,
+    CONSTRAINT fk_pl_line FOREIGN KEY (lineId)
+        REFERENCES `lines`(id) ON DELETE CASCADE
+);