refactor: complete structlog migration with contextvars, kwargs, and logging hardening

- Add ContextVarsMiddleware for automatic user_id/chat_id/username binding
  via structlog contextvars (aiogram) and http_method/http_path (FastAPI)
- Use bound_contextvars() context manager instead of clear_contextvars()
  to safely restore previous state instead of wiping all context
- Register ContextVarsMiddleware as outermost middleware (before GlobalError)
  so all error logs include user context
- Replace structlog.get_logger() with structlog.get_logger(__name__) across
  270 calls in 265 files for meaningful logger names
- Switch wrapper_class from BoundLogger to make_filtering_bound_logger()
  for pre-processor level filtering (performance optimization)
- Migrate 1411 %-style positional arg logger calls to structlog kwargs
  style across 161 files via AST script
- Migrate log_rotation_service.py from stdlib logging to structlog
- Add payment module prefixes to TelegramNotifierProcessor.IGNORED_LOGGER_PREFIXES
  and ExcludePaymentFilter.PAYMENT_MODULES to prevent payment data leaking
  to Telegram notifications and general log files
- Fix LoggingMiddleware: add from_user null-safety for channel posts,
  switch time.time() to time.monotonic() for duration measurement
- Remove duplicate logger assignments in purchase.py, config.py,
  inline.py, and admin/payments.py

app/utils/button_styles_cache.py

@@ -5,12 +5,13 @@ by keeping the cache and its helpers in a dedicated module.
 """
 
 import json
-import logging
+
+import structlog
 
 from app.database.database import AsyncSessionLocal
 
 
-logger = logging.getLogger(__name__)
+logger = structlog.get_logger(__name__)
 
 # ---- Defaults per section ------------------------------------------------
 
@@ -116,5 +117,5 @@ async def load_button_styles_cache() -> dict[str, dict]:
         logger.exception('Failed to load button styles from DB, using defaults')
 
     _cached_styles = merged
-    logger.info('Button styles cache loaded: %s', list(merged.keys()))
+    logger.info('Button styles cache loaded', list=list(merged.keys()))
     return merged