♲ Refactor configuration to use viper with context propagation

- Replace global ConfigPath and Overrides with viper-based configuration
- Add viper.New() to create configurable viper instances
- Store viper and unmarshaled Config struct in context for testability
- Add RetrieveFromContext and AddToContext helper functions
- Update files.Append to accept context and retrieve config from it
- Update formatters.Preferred and formatters.New to accept context
- Add PersistentPreRunE in CLI to create and configure viper instance
- Support -c flag for custom config file path
- Support -v flag for config value overrides
- Update all test files to create viper and add to context
- Remove unused config types and load functions
- Add viper as dependency with automatic env var support (MYLOG_*)

formatters/null.go

@@ -1,11 +1,10 @@
 package formatters
 
 import (
-	"codeberg.org/danjones000/my-log/config"
 	"codeberg.org/danjones000/my-log/models"
 )
 
-func newNull(ff config.Formatters) (Formatter, error) {
+func newNull(ff map[string]any) (Formatter, error) {
 	return &Null{}, nil
 }