Make monster HP primary in encounter lists and difficulty display

[Daren9m]

Problem

XP is currently the most prominent per-monster and difficulty-meter value, but HP is more useful to a DM preparing and running the battle.

Acceptance criteria

• Each monster row prominently displays total HP for the quantity in the encounter, with per-creature HP still clear.
• Total monster HP is prominent in the encounter summary.
• The difficulty display emphasizes monster HP and the five-level risk category rather than raw XP.
• XP remains available as secondary rules/reference information where useful.
• Quantity changes update all HP totals immediately.