✨ Add ANSI color mode

docs/changes/0.4.0.md

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+## BitLogger Update Changes
+
+version 0.4.0
+
+### Feature
+
+- feat: add `ColorMode = Never | Auto | Always` for text formatter color control
+- feat: add ANSI level, target, timestamp, and field rendering to `format_text(...)`
+- feat: add `color_mode` to `TextFormatter` and `TextFormatterConfig`
+- feat: support `text_formatter.color_mode` in JSON config parsing and serialization
+
+### Test
+
+- test: cover ANSI text formatter rendering in `Always` mode
+- test: cover `Auto` mode fallback behavior when `NO_COLOR` is present
+- test: cover config parsing and serialization for `color_mode`
+
+### Example
+
+- docs: add `color_mode` usage examples to formatter documentation
+
+### Notes
+
+- `Auto` currently uses a conservative rule: if `NO_COLOR` exists, ANSI is disabled; otherwise ANSI is enabled
+- this batch only covers ANSI formatter output and does not yet include inline style markup or tag registry support