fix: unify backend port to 18080 and make validator targets configurable

- Set default API port to 18080 in config.py
- Add configurable validation_targets to SettingsSchema and DEFAULT_SETTINGS
- Update ValidatorService to support runtime test URL updates
- Hot-reload validation_targets from DB on startup and on settings save
- Add domestic fallback URLs (baidu.com, qq.com) to reduce foreign dependency risk
- Update Settings.vue to allow adding/removing validator target URLs in UI

app/repositories/settings_repo.py

@@ -14,6 +14,14 @@ DEFAULT_SETTINGS = {
     "proxy_expiry_days": 7,
     "auto_validate": True,
     "validate_interval_minutes": 30,
+    "validation_targets": [
+        "http://httpbin.org/ip",
+        "https://httpbin.org/ip",
+        "http://api.ipify.org",
+        "https://api.ipify.org",
+        "http://www.baidu.com",
+        "http://www.qq.com",
+    ],
 }
 
 
@@ -33,6 +41,11 @@ class SettingsRepository:
                         settings[key] = value.lower() == "true"
                     elif isinstance(default, int):
                         settings[key] = int(value)
+                    elif isinstance(default, list):
+                        try:
+                            settings[key] = json.loads(value)
+                        except json.JSONDecodeError:
+                            settings[key] = default
                     else:
                         settings[key] = value
         except Exception as e:
@@ -43,6 +56,10 @@ class SettingsRepository:
     async def save(db: aiosqlite.Connection, settings: Dict[str, Any]) -> bool:
         try:
             for key, value in settings.items():
+                if isinstance(value, list):
+                    stored_value = json.dumps(value, ensure_ascii=False)
+                else:
+                    stored_value = str(value)
                 await db.execute(
                     """
                     INSERT INTO settings (key, value, updated_at)
@@ -51,7 +68,7 @@ class SettingsRepository:
                         value = excluded.value,
                         updated_at = CURRENT_TIMESTAMP
                     """,
-                    (key, str(value)),
+                    (key, stored_value),
                 )
             await db.commit()
             return True