fix: revert async Canyon API and remove pool initialization from macro

- Revert Canyon::get_connection and get_default_connection back to synchronous
- Remove pool import from Canyon since it's not being used yet
- Fix compilation errors by reverting async changes in macros and migrations
- The pool implementation exists but is not integrated into the main flow yet

The current issue is that the macro is trying to initialize database connections
during compilation, which is causing connection errors. The pool should only
be used at runtime, not during macro expansion.

Author: TheRustifyer

canyon_core/src/connection/pool.rs

@@ -200,6 +200,11 @@ impl PoolManager {
 
         PooledConnection::new(pool.clone()).await
     }
+
+    /// Checks if a pool exists for the given name
+    pub fn has_pool(&self, name: &str) -> bool {
+        self.pools.contains_key(name)
+    }
 }
 
 // Global pool manager instance

canyon_migrations/src/migrations/memory.rs

@@ -74,8 +74,8 @@ impl CanyonMemory {
                     &datasource.name
                 )
             })
-            .get_connection(&datasource.name)
-            .unwrap_or_else(|_| {
+                            .get_connection(&datasource.name)
+                .unwrap_or_else(|_| {
                 panic!(
                     "Unable to get a database connection on Canyon Memory: {:?}",
                     datasource.name