docs: explain colorize must be a format, not a Console option

[TrueFurina]

Summary

Per #1095: users try colorize: true as a Console transport option and see no colors. Documents that colorize is a format, not a transport option.

Changes

• docs/transports.md: new "#### Colorizing Console output" subsection under the Console Transport section:
  • states plainly that colorize is a format and must be composed into format (logger or transport level)
  • shows a working combine(colorize(), timestamp(), printf(...)) example
  • warns that colorize() placed after a printf/message-composing formatter has no visible effect, matching the root cause in the issue (colors applied to the already-final message)

Verification

• Example matches the working resolution in the issue comments (colorize as format, first in the combine chain)