fix: Rename Plugin_config methods to avoid conflict with CodeIgniter Model::set()

The PluginConfig class extends CodeIgniter\Model which has its own set() method
for query building. Renaming get()/set() to getValue()/setValue() avoids this conflict.

Also fixed:
- batchSave() to use setValue() instead of set()
- Updated all callers in PluginManager and BasePlugin to use renamed methods

app/Models/PluginConfig.php

@@ -23,7 +23,7 @@ class PluginConfig extends Model
         return ($builder->get()->getNumRows() === 1);
     }
 
-    public function get(string $key): ?string
+    public function getValue(string $key): ?string
     {
         $builder = $this->db->table('plugin_config');
         $query = $builder->getWhere(['key' => $key], 1);
@@ -35,7 +35,7 @@ class PluginConfig extends Model
         return null;
     }
 
-    public function set(string $key, string $value): bool
+    public function setValue(string $key, string $value): bool
     {
         $builder = $this->db->table('plugin_config');
         
@@ -84,7 +84,7 @@ class PluginConfig extends Model
         $this->db->transStart();
 
         foreach ($data as $key => $value) {
-            $success &= $this->set($key, $value);
+            $success &= $this->setValue($key, $value);
         }
 
         $this->db->transComplete();