refactor: migrate logging calls to stdlib logging.getLogger() pattern

[kvithayathil]

Context

The codebase uses structlog.get_logger(__name__) directly in 35+ files. The idiomatic structlog pattern is to call logging.getLogger(__name__) (stdlib) with structlog's ProcessorFormatter handling formatting underneath. This decouples callers from structlog entirely — they only import logging, and structlog configuration is centralized.

Task

1. Enable structlog.stdlib.LoggerFactory() in configure_logger() (currently commented out at app_logger.py:109)
2. Ensure ProcessorFormatter is wired for all stdlib log handlers
3. Replace structlog.get_logger(__name__) → logging.getLogger(__name__) across all 35+ files
4. Replace from app.utils.app_logger import logger → logging.getLogger(__name__) (2 files)
5. Update AppLogger class to use stdlib-first pattern internally
6. Run full test suite + basedpyright to verify no regressions

Acceptance Criteria

• All callers use logging.getLogger(__name__) — zero direct structlog imports in application code
• structlog configuration remains in app_logger.py only
• All 1213+ tests pass
• basedpyright clean

Files

• app/logger_config/app_logger.py — enable LoggerFactory, fix configuration
• 35+ files across app/ — replace import pattern
• app/utils/app_logger.py — update or remove shared logger