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/12_platforms_trigger.sql

@@ -0,0 +1,13 @@
+CREATE TRIGGER IF NOT EXISTS trg_platforms_before_insert
+    BEFORE INSERT ON `platforms`
+        FOR EACH ROW
+            BEGIN
+                SET NEW.location = POINT(NEW.longitude, NEW.latitude);
+        END;
+
+CREATE TRIGGER IF NOT EXISTS trg_platforms_before_update
+    BEFORE UPDATE ON `platforms`
+        FOR EACH ROW
+            BEGIN
+                SET NEW.location = POINT(NEW.longitude, NEW.latitude);
+        END;