fix(installer): ensure system site-packages has priority over server-libs

Add priority parameter to import_package_bundle that uses sys.path.insert(0)
to place packages at the front of sys.path. System site-packages now uses
this priority flag to ensure user-installed packages are found before
bundled server-libs packages.

Author: mfranczel

installer/__main__.py

@@ -273,7 +273,7 @@ def bootstrap():
     venv.import_package_bundle(
         server_site_packages_path, condition_env="DEEPNOTE_INCLUDE_SERVER_PACKAGES"
     )
-    venv.import_package_bundle(system_site_packages_path)
+    venv.import_package_bundle(system_site_packages_path, priority=True)
     venv.import_package_bundle(kernel_site_package_path)
 
     # Phase 7.2: Symlink notebook to jupyter_server for compatibility with

installer/module/virtual_environment.py

@@ -81,31 +81,40 @@ def start_server(self, command: str, cwd: Optional[str] = None) -> ServerProcess
         return server_proc
 
     def import_package_bundle(
-        self, bundle_site_package_path: str, condition_env: Optional[str] = None
+        self, bundle_site_package_path: str, 
+        condition_env: Optional[str] = None,
+        priority: bool = False,
     ) -> None:
         """
         Import a package bundle to the virtual environment.
 
         :param bundle_site_package_path: Absolute path to the package bundle.
         :param condition_env: Optional environment variable name. If provided, the bundle
-                         will only be loaded when this env var is set to 'true'.
+                        will only be loaded when this env var is set to 'true'.
+        :param priority: If True, insert at front of sys.path to override other bundles.
         """
         pth_file_path = os.path.join(self._site_packages_path, "deepnote.pth")
 
         with open(pth_file_path, "a+", encoding="utf-8") as pth_file:
             if condition_env:
                 # Write conditional import that checks environment variable
                 pth_content = (
-                    f"import sys, os, sysconfig; "
-                    f"(sys.path.append('{bundle_site_package_path}'), "
-                    f"sys.path.insert(sys.path.index('{bundle_site_package_path}'), sysconfig.get_path('purelib'))) "
+                    f"import os, sys; "
+                    f"sys.path.insert(0, '{bundle_site_package_path}') "
                     f"if os.environ.get('{condition_env}', '').lower() == 'true' else None"
                 )
                 pth_file.write(pth_content + "\n")
                 logger.info(
                     "Bundle was conditionally imported to the virtual environment "
                     f"(loads when {condition_env}=true)."
                 )
+            elif priority:
+                # Insert at front of sys.path for higher priority (overrides other bundles)
+                pth_content = f"import sys; sys.path.insert(0, '{bundle_site_package_path}')"
+                pth_file.write(pth_content + "\n")
+                logger.info(
+                    "Bundle was imported with priority to the virtual environment."
+                )
             else:
                 pth_file.write(bundle_site_package_path + "\n")
                 logger.info(