Fix bare except clauses for better error handling

Replace 5 bare except clauses with 'except Exception:' to improve
error handling and prevent catching system exits and keyboard interrupts:

- gui.py:155 - Queue event processing
- setup_wizard.py:184 - API response parsing
- test_credentials.py:213 - Response JSON parsing
- test_credentials.py:240 - Error response parsing
- test_credentials.py:257 - Response text formatting

This change improves code quality and follows Python best practices
for exception handling.

gui.py

@@ -152,7 +152,7 @@ class Dashboard:
                 try:
                     msg = self.event_queue.get_nowait()
                     self.window["-LOG-"].print(msg)
-                except:
+                except Exception:
                     break
 
             # Update statistics

setup_wizard.py

@@ -181,7 +181,7 @@ async def validate_perplexity_key(api_key, model="sonar-pro"):
                             print_warning(f"400 Fehler: {error_msg}")
                             print_info("Fahre trotzdem fort - bitte später manuell prüfen!")
                             return (True, False, model)
-                    except:
+                    except Exception:
                         print_warning(f"Unerwartete Antwort: {response.status_code}")
                         print_info("Fahre trotzdem fort - bitte später manuell prüfen!")
                         return (True, False, model)

test_credentials.py

@@ -210,7 +210,7 @@ async def test_perplexity_key(api_key, model="sonar-pro"):
                         if "choices" in data and len(data["choices"]) > 0:
                             content = data["choices"][0]["message"]["content"]
                             print_info(f"Test response: '{content}'")
-                    except:
+                    except Exception:
                         pass
 
                     return True, test_model
@@ -237,7 +237,7 @@ async def test_perplexity_key(api_key, model="sonar-pro"):
                                 continue
                         else:
                             print_info(f"Error details: {error_msg}")
-                    except:
+                    except Exception:
                         print_warning(f"400 Bad Request (couldn't parse error)")
 
                     # If this was the last model, fail
@@ -254,7 +254,7 @@ async def test_perplexity_key(api_key, model="sonar-pro"):
                     print_warning(f"Unexpected status code: {response.status_code}")
                     try:
                         print_info(f"Response: {response.text[:200]}")
-                    except:
+                    except Exception:
                         pass
 
                     # Try next model if available