refactor(chat): deploy Turnfold without a submodule

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "chat/app"]
-	path = chat/app
-	url = https://github.com/liooil/turnfold.git

chat/README.md

@@ -1,17 +1,12 @@
 # Turnfold deployment
 
-The application source is maintained in the public
-[`liooil/turnfold`](https://github.com/liooil/turnfold) repository and mounted here
-as the `app` Git submodule. This directory only keeps xiteng.site-specific
-deployment configuration and the local provider bridge.
+The application source is maintained independently in the public
+[`liooil/turnfold`](https://github.com/liooil/turnfold) repository. This
+directory only keeps xiteng.site-specific deployment configuration and the
+local provider bridge. The Compose build context pins an exact Turnfold commit
+from GitHub; this repository intentionally does not use a Git submodule.
 
-After cloning the homelab repository, initialize the application source with:
-
-```sh
-git submodule update --init chat/app
-```
-
-To deploy the pinned Turnfold revision:
+To deploy the pinned Turnfold revision directly from GitHub:
 
 ```sh
 docker compose -f chat/compose.yml up -d --build

chat/compose.yml

@@ -85,7 +85,7 @@ services:
 
   chat:
     build:
-      context: ./app
+      context: "https://github.com/liooil/turnfold.git?ref=main&checksum=181d95fa2e55dbbe10e143921894ef0e7eda3be6"
       args:
         BASE_PATH: /chat
         HOME_URL: /