Replace shared_lib submodule with shared for decoupling deploy

- Swap shared_lib submodule → shared (tracking decoupling branch)
- Dockerfile: shared_lib/ → shared/, remove bp symlink hack
- CI: trigger on decoupling branch, use dynamic ref_name

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -2,7 +2,7 @@ name: Build and Deploy
 
 on:
   push:
-    branches: [main]
+    branches: [main, decoupling]
 
 env:
   REGISTRY: registry.rose-ash.com:5000
@@ -36,8 +36,8 @@ jobs:
         run: |
           ssh "root@$DEPLOY_HOST" "
             cd ${{ env.REPO_DIR }}
-            git fetch origin main
-            git reset --hard origin/main
+            git fetch origin ${{ github.ref_name }}
+            git reset --hard origin/${{ github.ref_name }}
             git submodule update --init --recursive
           "