Add customizable titlebar clock format

[midwan]

Summary

• Add a configurable titlebar clock format stored in the environment config.
• Use locale.library FormatDate for custom clock strings and locale AM/PM text for the default 12-hour clock.
• Add a Clock Format picker in Environment > Locale with supported FormatDate tokens.
• Keep the OS3 titlebar clock right-aligned while avoiding the startup freezes seen in the earlier screen-title path.

Validation

• python3 -m unittest discover source/Modules/configopus/tests
• python3 -m unittest discover source/Program/tests
• python3 -m unittest discover source/Library/tests
• git diff --check
• podman run --rm -v /home/midwan/Github/dopus5:/work -w /work/source sacredbanana/amiga-compiler:m68k-amigaos make os3 all debug=no
• podman run --rm -v /home/midwan/Github/dopus5:/work -w /work/source sacredbanana/amiga-compiler:m68k-amigaos make os3 release-package debug=no

Refs #109

[chatgpt-codex-connector]

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