Coop lockout fix, holidays full list, !fx convert, lottery cleanup

- Co-op: when a run wipes or completes, clear the 99-sentinel combat
  lock for participants and pin combat_actions_used to maxCombatActions.
  Previously the lock only released on the next midnight reset, so
  members were stuck unable to combat for the rest of the day after
  their run ended.
- Holidays: !holidays now prints the full list. Previously it called
  the same featured-only formatter as TwinBee's morning auto-post,
  so users saw the same truncated message twice with a misleading
  "Use !holidays for the full list" hint that pointed at itself.
- Forex: add currency conversion. Auto-detects when the first arg is
  numeric (`!fx 1500 USD EUR`) and also accepts an explicit `convert`
  subcommand. Tolerant parsing: "to"/"into"/"in"/"=" filters, comma
  and k/m suffix support, and any of `1500 USD EUR`, `1500 USD/EUR`,
  `USD/EUR 1500` orderings. Includes parser + comma-formatter tests.
- Lottery: drop 2-match prize tier. At 1/16 odds × €25 it was +EV per
  ticket on its own and bled the community pot (~€775/wk recently),
  preventing jackpot rollover from accumulating. Removed from scoring,
  payout loops, draw announcement, !lottery odds, and !lottery history.
  Match2Winners DB column kept (history rows preserved); always written
  as 0 going forward.
- Lottery: shift week boundary so Sat/Sun return next Monday. Friday's
  23:59 draw used to leave players locked at their 100-ticket cap until
  next Monday rolled in; now the cap resets immediately after the draw.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/adventure_npcs.go

@@ -268,7 +268,9 @@ func (p *AdventurePlugin) resolveArina(ctx MessageContext, char *AdventureCharac
 		if err := saveAdvCharacter(char); err != nil {
 			slog.Error("npc: failed to save arina buff", "user", ctx.Sender, "err", err)
 		}
-		return p.SendDM(ctx.Sender, fmt.Sprintf("_%s_", arinaAcceptLine))
+		return p.SendDM(ctx.Sender, fmt.Sprintf(
+			"_She snatches the money from you, almost rudely, then looks at you expectantly._\n\n\"%s\"\n\n_She walks away just as quickly as she came._",
+			arinaAcceptLine))
 	}
 
 	// Declined — no mechanical effect, just insults