Remember capitalization changed with shift

[4di-hello]

Builds on #607 (change capitalization of the typed word with shift). When the user changes a word the same way twice (e.g. du → Du, abc → ABC), it is written like this automatically from then on.

• Applied like an auto-correction: backspace reverts it, and also forgets the learned form
• Settings entry lists all learned forms, each can be removed, or all at once
• Only available when "shift changes capitalization" is enabled; off by default
• Nothing is learned in incognito mode, not applied in password fields
• At most 300 entries, stored in the app preferences
• Unit test included

[LeanBitLab]

Thank you for the thoughtful implementation and tests!

While the concept of learned casing is interesting, storing up to 300 custom casing entries in preferences, adding a dedicated management dialog, and altering word capitalization on commit adds substantial state complexity. More importantly, it risks surprising normal users with unexpected casing alterations during everyday typing where predictable dictionary behavior is expected.

To preserve typing predictability, engine simplicity, and avoid settings bloat, we are leaning against introducing learned casing management into core typing.

[4di-hello]

Thanks for the review. Closing this, I'll keep it in my fork.