Subscribe form upgrades and layout fixes

• Added subscribe form notice text with rich text support and an optional consent checkbox.

• Improved form styling inside content areas, including better button alignment for form layouts.

• Improved heading wrapping with balanced text.

• Applied the theme accent color to native form controls in content areas.

• Fixed search block alignment issues in rendered layouts.

• Fixed stacked author image presentation on post cards and post pages.

• Fixed untranslated interface strings in exported themes.

• Fixed mobile menu logo focus outline.

• Fixed section card columns hiding when a background image is enabled.