initial NextChair Manager.

Key additions:
* Separate platform Manager stack: [stacks/manager/compose.yaml]
* Dedicated manager authentication with signed sessions.
* Business overview dashboard.
* Add Business workflow with slug suggestions and deployment progress.
* Business detail page with start, stop, restart, update, logs, Dockge, and conservative removal actions.
* Explicit management API endpoints under [src/app/api/manager]
* Shared provisioning service layer in [provisioning.service.ts]
* CLI and UI now use the same [create-business.sh] provisioning logic.
* Registry metadata, database status, container health, and media usage reporting.
* Manager-only entrypoint mode that does not require a business database.
* Updated deployment documentation with Manager setup and Caddy routing.
Validation passed:
* Infra, Caddy, Manager, and generated business Compose configurations.
* Shell syntax checks.
* Registry generation with registry image tags.
* git diff --check.

stacks/manager/compose.yaml

@@ -0,0 +1,24 @@
+name: nextchair-manager
+
+# Platform administration is its own application stack. It shares only the
+# private proxy network with Caddy and uses no business database.
+
+services:
+  nextchair-manager:
+    image: ${NEXTCHAIR_IMAGE:-nextchair:latest}
+    container_name: nextchair-manager
+    restart: unless-stopped
+    env_file:
+      - .env
+    environment:
+      MANAGER_MODE: "true"
+    volumes:
+      - ../:/app/stacks
+      - ../../.env.infra:/app/.env.infra:ro
+    networks:
+      - nextchair-proxy
+
+networks:
+  nextchair-proxy:
+    name: nextchair-proxy
+    external: true