Migrate omsorgapp to browser SPA, add Docker/CI build setup

- omsorgapp: drop Electron, run as a plain Vite/React browser app; refresh
  token moves to an HttpOnly cookie (omsorgCore), CORS added for the new
  browser origin, document download/preview switched to Blob-based browser
  APIs.
- Add Dockerfiles for omsorgCore, omsorgapp, and omsorgWeb, a docker-compose.yml
  wiring Postgres/MySQL/all three apps together, and a Gitea Actions workflow
  that builds and pushes images to the repo's container registry on push to
  main and on version tags.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,101 @@
+name: omsorg
+
+# WICHTIG (der fehleranfälligste Punkt in diesem Setup):
+# - omsorgapp.build.args.VITE_OMSORG_CORE_URL muss die vom BROWSER erreichbare Adresse von
+#   omsorgcore sein (hier: der auf dem Host published Port), NICHT der interne Compose-DNS-Name -
+#   Vite bäckt diese URL zur Build-Zeit in den JS-Bundle ein (siehe omsorgapp/src/api/config.js).
+# - omsorgweb.environment.OMSORG_CORE_URL ist dagegen der interne Servicename (http://omsorgcore:8080),
+#   da PHP dort serverseitig per cURL aufruft (kein Browser-Kontext), siehe
+#   omsorgWeb/docker/bootstrap-config.php.
+
+services:
+  postgres:
+    image: postgres:16
+    environment:
+      POSTGRES_DB: omsorg_core
+      POSTGRES_USER: omsorg_core
+      POSTGRES_PASSWORD: omsorg_core_dev_password
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U omsorg_core"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+
+  mysql:
+    image: mysql:8.0
+    environment:
+      MYSQL_DATABASE: omsorg_web
+      MYSQL_USER: omsorg_web
+      MYSQL_PASSWORD: omsorg_web_dev_password
+      MYSQL_ROOT_PASSWORD: omsorg_web_root_dev_password
+    volumes:
+      - mysql_data:/var/lib/mysql
+    healthcheck:
+      test: ["CMD", "mysqladmin", "ping", "-h", "localhost"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+
+  omsorgcore:
+    build:
+      context: .
+      dockerfile: omsorgCore/Dockerfile
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      ASPNETCORE_ENVIRONMENT: Development
+      ConnectionStrings__OmsorgCore: "Host=postgres;Port=5432;Database=omsorg_core;Username=omsorg_core;Password=omsorg_core_dev_password"
+      Jwt__Secret: "CHANGE_ME_LOCAL_DEV_SECRET_MIN_32_CHARS_LONG"
+      Cors__AllowedOrigins__0: "http://localhost:5173"
+    ports:
+      - "8080:8080"
+    volumes:
+      - omsorgcore_documents:/app/App_Data/documents
+
+  omsorgapp:
+    build:
+      context: .
+      dockerfile: omsorgapp/Dockerfile
+      args:
+        VITE_OMSORG_CORE_URL: "http://localhost:8080"
+    ports:
+      - "5173:80"
+    depends_on:
+      - omsorgcore
+
+  omsorgweb:
+    build:
+      context: .
+      dockerfile: omsorgWeb/Dockerfile
+    depends_on:
+      mysql:
+        condition: service_healthy
+      omsorgcore:
+        condition: service_started
+    environment:
+      DB_HOST: mysql
+      DB_NAME: omsorg_web
+      DB_USER: omsorg_web
+      DB_PASSWORD: omsorg_web_dev_password
+      OMSORG_CORE_URL: "http://omsorgcore:8080"
+    ports:
+      - "8081:80"
+    volumes:
+      - web_uploads:/var/www/html/mitarbeiter-app-legacy/uploads
+      - web_downloads:/var/www/html/mitarbeiter-app-legacy/downloads
+      - web_fortbildung:/var/www/html/mitarbeiter-app-legacy/fortbildung-materials
+      - web_avatars:/var/www/html/mitarbeiter-app-legacy/assets/avatars
+      - web_data:/var/www/html/mitarbeiter-app-legacy/data
+
+volumes:
+  postgres_data:
+  mysql_data:
+  omsorgcore_documents:
+  web_uploads:
+  web_downloads:
+  web_fortbildung:
+  web_avatars:
+  web_data: