Make evidence text a full-screen reading mode

[jonashertner]

Outcome

• adds an explicit full-screen reading surface with a persistent return to the map
• opens legal review, feature details, and the first-visit project brief in the same predictable reading mode
• removes nested text scrolling and improves typography, scrollbar visibility, and narrow-screen fit
• keeps the map workspace intact and adds a concise translated Read action

Validation

• npm run release
• npm run check:links
• git diff --check
• Chrome QA at 1440×900, 844×390, 390×844, and 320×568
• checked map, manual reading, legal review, feature detail, and first-visit brief in all five languages