Feature/memory optimization config (#108)

* feat(config): optimize memory usage to prevent OOM killer

- Reduce brightness from 95 to 50 to lower power consumption
- Reduce refresh rate from 120Hz to 100Hz to reduce CPU/memory pressure
- Reduce background service workers from 3 to 1 per manager
- Change hardware mapping from adafruit-hat-pwm to adafruit-hat
- Expected memory savings: ~700MB reduction in background service usage
- Addresses SIGKILL errors caused by memory exhaustion on Raspberry Pi

Fixes: OOM killer terminating ledmatrix.service with status=9/KILL

* revert display brightness

* refactor(background-service): hardcode optimized settings and remove config blocks

- Hardcode background service to 1 worker in all managers
- Remove background_service config blocks from template
- Simplify configuration for users - no need to adjust system settings
- Memory optimization: ~700MB reduction in background service usage
- Settings: 1 worker, 30s timeout, 3 retries (hardcoded)

Files updated:
- src/base_classes/sports.py
- src/leaderboard_manager.py
- src/odds_ticker_manager.py
- src/soccer_managers.py
- src/milb_manager.py
- config/config.template.json

This prevents OOM killer errors by reducing memory usage from
15 background threads to 5 threads total across all managers.

* remove fallback in case of background service failure

src/base_classes/sports.py

@@ -105,19 +105,12 @@ class SportsCore(ABC):
         self._rankings_cache_timestamp = 0
         self._rankings_cache_duration = 3600  # Cache rankings for 1 hour
 
-        # Initialize background data service
-        background_config = self.mode_config.get("background_service", {})
-        if background_config.get("enabled", True):  # Default to enabled
-            max_workers = background_config.get("max_workers", 3)
-            self.background_service = get_background_service(self.cache_manager, max_workers)
-            self.background_fetch_requests = {}  # Track background fetch requests
-            self.background_enabled = True
-            self.logger.info(f"Background service enabled with {max_workers} workers")
-        else:
-            self.background_service = None
-            self.background_fetch_requests = {}
-            self.background_enabled = False
-            self.logger.info("Background service disabled")
+        # Initialize background data service with optimized settings
+        # Hardcoded for memory optimization: 1 worker, 30s timeout, 3 retries
+        self.background_service = get_background_service(self.cache_manager, max_workers=1)
+        self.background_fetch_requests = {}  # Track background fetch requests
+        self.background_enabled = True
+        self.logger.info("Background service enabled with 1 worker (memory optimized)")
 
     def _get_season_schedule_dates(self) -> tuple[str, str]:
         return "", ""