fix: task 7 — production hardening quick fixes

- Replace 4 bare `except:` with `except Exception:` (load_settings,
  get_txt, get_icon_idx_for_file, process_file cleanup block) so
  SystemExit and KeyboardInterrupt are no longer swallowed
- Replace 2 print() calls with logger.error() (__init__ MSAL init,
  ensure_valid_token) so errors appear in the configurable log output
- Sanitize item['name'] with os.path.basename() in on_download_clicked
  and _download_folder_recursive_sync to prevent path traversal from
  server-controlled filenames
- Add 8 new unit tests covering all Task 7 changes

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

sharepoint_browser.py

@@ -67,7 +67,7 @@ def load_settings():
     with open(SETTINGS_FILE, 'r', encoding='utf-8') as f:
         try:
             return json.load(f)
-        except:
+        except Exception:
             return default_settings
 
 def save_settings(new_settings):
@@ -708,7 +708,7 @@ class SharePointApp(wx.Frame):
             try:
                 self.msal_app = msal.PublicClientApplication(CLIENT_ID, authority=AUTHORITY)
             except Exception as e:
-                print(f"MSAL Init Error: {e}")
+                logger.error(f"MSAL Init Error: {e}")
         
         self.InitUI()
         self.Centre()
@@ -737,7 +737,7 @@ class SharePointApp(wx.Frame):
         if kwargs:
             try:
                 return text.format(**kwargs)
-            except:
+            except Exception:
                 pass
         return text
 
@@ -1303,7 +1303,7 @@ class SharePointApp(wx.Frame):
             with wx.DirDialog(self, self.get_txt("msg_select_folder"), style=wx.DD_DEFAULT_STYLE | wx.DD_DIR_MUST_EXIST) as dd:
                 if dd.ShowModal() == wx.ID_OK:
                     parent_path = dd.GetPath()
-                    dest_path = os.path.join(parent_path, item['name'])
+                    dest_path = os.path.join(parent_path, os.path.basename(item['name']))
                     threading.Thread(target=self._download_folder_bg_task, args=(item, dest_path), daemon=True).start()
 
     def _download_file_bg_task(self, item, dest_path):
@@ -1343,7 +1343,7 @@ class SharePointApp(wx.Frame):
                 res_data = res.json()
                 items = res_data.get('value', [])
                 for item in items:
-                    item_path = os.path.join(local_dir, item['name'])
+                    item_path = os.path.join(local_dir, os.path.basename(item['name']))
                     if 'folder' in item:
                         self._download_folder_recursive_sync(drive_id, item['id'], item_path)
                     else:
@@ -1666,7 +1666,7 @@ class SharePointApp(wx.Frame):
                 self.headers = {'Authorization': f'Bearer {self.access_token}'}
                 return True
         except Exception as e:
-            print(f"Token refresh error: {e}")
+            logger.error(f"Token refresh error: {e}")
             
         self.set_status(self.get_txt("status_login_needed"))
         return False
@@ -2073,7 +2073,7 @@ class SharePointApp(wx.Frame):
                             idx = self.image_list.Add(bmp)
                             self.ext_icons[ext] = idx
                             return idx
-        except:
+        except Exception:
             pass
 
         self.ext_icons[ext] = self.idx_file
@@ -2410,7 +2410,7 @@ class SharePointApp(wx.Frame):
             try:
                 os.remove(local_path)
                 os.rmdir(working_dir)
-            except:
+            except Exception:
                 pass
                 
             self.set_status(self.get_txt("msg_update_success", name=file_name))