Improve japanese layout

• The button-styling has been adjusted, to make it easier to visually distinguish the view-changing buttons that switch to views with buttons for entering hiragana, katakana, symbols, and Latin letters.

• Easier switching between hiragana and katakana, and between symbols and punctuation.

• Added more placeholders to prevent layout-shifting.

• The base-shape is now sized properly on a 6" large display with a resolution of 720x1440 (PinePhone), without empty space next to it.

• The wide shape is now wider.

• The symbols- and punctuation-views switch back to the katakana-view when opened from it and "unlocking" the view by tapping multiple times on the view-changing button, instead of showing the hiragana-view.

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Screenshots - before this change

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Screenshots - after this change

Adwaita:dark

HighContrast

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