feat: separate create/edit form pages, Playwright test infrastructure, /auth/token endpoint

Move all CRUD create/edit forms from inline on list pages to dedicated form pages
with back-button navigation and post-save redirect. Add Playwright Docker container
(browser server on port 3000) with 25 passing E2E tests covering login, navigation,
and site CRUD workflows. Add POST /auth/token endpoint for clean JWT retrieval.

infra/docker-compose.yml

@@ -88,6 +88,20 @@ services:
       - scadalink-net
     restart: unless-stopped
 
+  playwright:
+    image: mcr.microsoft.com/playwright:v1.58.2-noble
+    container_name: scadalink-playwright
+    ports:
+      - "3000:3000"
+    command: >
+      npx -y playwright@1.58.2 run-server
+      --host 0.0.0.0
+      --port 3000
+    ipc: host
+    networks:
+      - scadalink-net
+    restart: unless-stopped
+
 volumes:
   scadalink-mssql-data: