v0.7.25 - Implement SQL Query Admin API

- Move non-NIP-17 admin functions from dm_admin.c to api.c for better architecture
- Add NIP-44 encryption to send_admin_response() for secure admin responses
- Implement SQL query validation and execution with safety limits
- Add unified SQL query handler for admin API
- Fix buffer size for encrypted content to handle larger responses
- Update function declarations and includes across files
- Successfully test frontend query execution through web interface

src/subscriptions.h

@@ -93,6 +93,7 @@ struct subscription_manager {
 };
 
 // Function declarations
+int validate_subscription_id(const char* sub_id);
 subscription_filter_t* create_subscription_filter(cJSON* filter_json);
 void free_subscription_filter(subscription_filter_t* filter);
 subscription_t* create_subscription(const char* sub_id, struct lws* wsi, cJSON* filters_array, const char* client_ip);