feat: add shared library as git submodule

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

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "shared_lib"]
+	path = shared_lib
+	url = https://git.rose-ash.com/coop/shared.git

app.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import path_setup  # noqa: F401  # adds shared_lib to sys.path
+
 from quart import g
 
 from shared.factory import create_base_app

path_setup.py

@@ -0,0 +1,7 @@
+import sys
+import os
+
+# Add the shared library submodule to the Python path
+_shared = os.path.join(os.path.dirname(os.path.abspath(__file__)), "shared_lib")
+if _shared not in sys.path:
+    sys.path.insert(0, _shared)