feat: Add settings module

- Add configuration for parallel processing
- Add optimization settings (optipng level, trim padding)
- Support environment variable overrides
- Add temporary directory prefix setting

settings.py

@@ -0,0 +1,18 @@
+"""Configuration settings for the PDF Musical Score Cleaner."""
+
+import os
+import multiprocessing
+
+# Number of parallel processes to use for operations that support parallelization
+# Defaults to number of CPU cores - 1, but never less than 1
+DEFAULT_PARALLEL_PROCESSES = max(1, multiprocessing.cpu_count() - 1)
+
+# Can be overridden by environment variable
+PARALLEL_PROCESSES = int(os.getenv('NOTES_CLEANER_PARALLEL_PROCESSES', DEFAULT_PARALLEL_PROCESSES))
+
+# Optimization settings
+OPTIPNG_OPTIMIZATION_LEVEL = int(os.getenv('NOTES_CLEANER_OPTIPNG_LEVEL', '7'))  # 0-7, higher = better compression but slower
+TRIM_PADDING_PIXELS = int(os.getenv('NOTES_CLEANER_TRIM_PADDING', '20'))  # Padding around content after trimming
+
+# Temporary directory settings
+TEMP_DIR_PREFIX = 'notes_cleaner_'