fix: make sure mutable test apps don't clash

The mock server is stateful and with multiple tests running either after
another (was getting issues with hello world being deployed when it
shouldn't have been), and also with parallel workers, I think it's
better we scope each test with their own unique hello_world app name.
`test_app` remains non-unique - it needs to be expected to be there (I
guess I could put it in the context, but it doesn't need to be yet so
🤷).

Other alternative was resetting the mock DB but I figured that might
lead to race conditions and it was better if this stuff was just as
idempotent as possible

Author: socksy

tests/integration/features/steps/mcp_steps.py

@@ -53,8 +53,13 @@ async def call_mcp_tool(context, tool_name, arguments=None):
 
 def create_towerfile(app_type="hello_world"):
     """Create a Towerfile for testing - pure function with no side effects beyond file creation"""
+    import uuid
+
+    # Add unique suffix to avoid test interference
+    unique_suffix = str(uuid.uuid4())[:8]
+
     configs = {
-        "hello_world": ("hello-world", "hello.py", "Simple hello world app"),
+        "hello_world": (f"hello-world-{unique_suffix}", "hello.py", "Simple hello world app"),
         "test_app": ("test-app", "hello.py", "Pre-existing test app for CLI tests"),
     }