fix(logging): move module-level initialization to explicit setup calls (#3874)

- Moved environment variable parsing and `setup_logging()` call from
module level to proper initialization points
- Added explicit `setup_logging()` calls in `server.py::create_app()`
and `library_client.py::AsyncLlamaStackAsLibraryClient.__init__()`

Module-level side effects are bad practice and can cause issues with
import order, testing, and circular dependencies. The previous
implementation ran logging setup on every import of the log module,
which is unpredictable and difficult to control.

---------

Co-authored-by: Claude <noreply@anthropic.com>

llama_stack/cli/llama.py

@@ -6,6 +6,8 @@
 
 import argparse
 
+from llama_stack.log import setup_logging
+
 from .stack import StackParser
 from .stack.utils import print_subcommand_description
 
@@ -42,6 +44,9 @@ class LlamaCLIParser:
 
 
 def main():
+    # Initialize logging from environment variables before any other operations
+    setup_logging()
+
     parser = LlamaCLIParser()
     args = parser.parse_args()
     parser.run(args)