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/mlb_manager.py

@@ -82,11 +82,6 @@ class BaseMLBManager(Baseball):
                     # Clear invalid cache
                     self.cache_manager.clear_cache(cache_key)
 
-        # If background service is disabled, fall back to synchronous fetch
-        if not self.background_enabled or not self.background_service:
-            pass
-            # return self._fetch_ncaa_api_data_sync(use_cache)
-
         self.logger.info(f"Fetching full {datestring} season schedule from ESPN API...")
 
         # Start background fetch