Feat v0.5.3 chat polish + integration testing

Conversation search (db.query search_like, chat-core /search endpoint,
sidebar search UI), message pagination polish (scroll preservation,
loading spinner), workflow-chat integration package, and multi-user
E2E test infrastructure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker-compose-e2e.yml

@@ -0,0 +1,87 @@
+# docker-compose-e2e.yml — Multi-replica E2E testing (Postgres)
+#
+# Two Switchboard replicas behind an nginx load balancer,
+# sharing a single Postgres instance. Tests cross-replica
+# broadcast via pg_notify.
+#
+# Usage:
+#   docker compose -f docker-compose-e2e.yml up --build -d
+#   ./ci/e2e-chat-test.sh
+#   docker compose -f docker-compose-e2e.yml down -v
+
+services:
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_DB: switchboard_e2e
+      POSTGRES_USER: switchboard
+      POSTGRES_PASSWORD: e2e-password
+    ports:
+      - "5432:5432"
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U switchboard -d switchboard_e2e"]
+      interval: 2s
+      timeout: 5s
+      retries: 10
+
+  switchboard-1:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    environment:
+      PORT: "8080"
+      BASE_PATH: ""
+      DB_DRIVER: postgres
+      DATABASE_URL: postgres://switchboard:e2e-password@postgres:5432/switchboard_e2e?sslmode=disable
+      JWT_SECRET: e2e-jwt-secret
+      ENCRYPTION_KEY: e2e-encryption-key-32chars!!!!!
+      SWITCHBOARD_ADMIN_USERNAME: admin
+      SWITCHBOARD_ADMIN_PASSWORD: admin
+      STORAGE_BACKEND: pvc
+      STORAGE_PATH: /data/storage
+      CORS_ALLOWED_ORIGINS: "*"
+      EXT_ALLOW_PRIVATE_IPS: "true"
+      LOG_FORMAT: text
+      LOG_LEVEL: info
+      SEED_USERS: "alice:password123:user,bob:password456:user,charlie:password789:user"
+    depends_on:
+      postgres:
+        condition: service_healthy
+    ports:
+      - "8081:80"
+
+  switchboard-2:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    environment:
+      PORT: "8080"
+      BASE_PATH: ""
+      DB_DRIVER: postgres
+      DATABASE_URL: postgres://switchboard:e2e-password@postgres:5432/switchboard_e2e?sslmode=disable
+      JWT_SECRET: e2e-jwt-secret
+      ENCRYPTION_KEY: e2e-encryption-key-32chars!!!!!
+      SWITCHBOARD_ADMIN_USERNAME: admin
+      SWITCHBOARD_ADMIN_PASSWORD: admin
+      STORAGE_BACKEND: pvc
+      STORAGE_PATH: /data/storage
+      CORS_ALLOWED_ORIGINS: "*"
+      EXT_ALLOW_PRIVATE_IPS: "true"
+      LOG_FORMAT: text
+      LOG_LEVEL: info
+      SEED_USERS: "alice:password123:user,bob:password456:user,charlie:password789:user"
+    depends_on:
+      postgres:
+        condition: service_healthy
+    ports:
+      - "8082:80"
+
+  lb:
+    image: nginx:alpine
+    volumes:
+      - ./ci/e2e-nginx.conf:/etc/nginx/nginx.conf:ro
+    ports:
+      - "3000:80"
+    depends_on:
+      - switchboard-1
+      - switchboard-2