refactor: implement lazy loading for coordinator-api service imports

Replaced eager imports with lazy loading using __getattr__ to defer service module imports until first access. Added module mapping dictionary and dynamic import logic to reduce initial import overhead while maintaining the same public API.

apps/coordinator-api/src/app/services/__init__.py

@@ -1,8 +1,23 @@
 """Service layer for coordinator business logic."""
 
-from .explorer import ExplorerService
-from .jobs import JobService
-from .marketplace import MarketplaceService
-from .miners import MinerService
+from importlib import import_module
 
 __all__ = ["JobService", "MinerService", "MarketplaceService", "ExplorerService"]
+
+_MODULE_BY_EXPORT = {
+    "ExplorerService": ".explorer",
+    "JobService": ".jobs",
+    "MarketplaceService": ".marketplace",
+    "MinerService": ".miners",
+}
+
+
+def __getattr__(name: str):
+    module_name = _MODULE_BY_EXPORT.get(name)
+    if module_name is None:
+        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+    module = import_module(module_name, __name__)
+    value = getattr(module, name)
+    globals()[name] = value
+    return value