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/forex_convert_test.go

@@ -0,0 +1,70 @@
+package plugin
+
+import "testing"
+
+func TestFxParseConvert(t *testing.T) {
+	cases := []struct {
+		in        []string
+		amt       float64
+		base      string
+		quote     string
+		shouldErr bool
+	}{
+		{[]string{"1500", "USD", "EUR"}, 1500, "USD", "EUR", false},
+		{[]string{"1500", "USD", "to", "EUR"}, 1500, "USD", "EUR", false},
+		{[]string{"1500", "USD", "into", "EUR"}, 1500, "USD", "EUR", false},
+		{[]string{"1,500.50", "USD", "EUR"}, 1500.50, "USD", "EUR", false},
+		{[]string{"1.5k", "USD", "EUR"}, 1500, "USD", "EUR", false},
+		{[]string{"1500", "USD/EUR"}, 1500, "USD", "EUR", false},
+		{[]string{"USD/EUR", "1500"}, 1500, "USD", "EUR", false},
+		{[]string{"1500", "EUR/USD"}, 1500, "EUR", "USD", false},
+		{[]string{"1500", "JPY", "USD"}, 1500, "JPY", "USD", false},
+
+		{[]string{"USD", "EUR"}, 0, "", "", true},                 // no amount
+		{[]string{"1500", "USD"}, 0, "", "", true},                // missing quote
+		{[]string{"1500", "USD", "USD"}, 0, "", "", true},         // same currency
+		{[]string{"1500", "ZZZ", "EUR"}, 0, "", "", true},         // unknown currency
+		{[]string{"1500", "USD", "EUR", "JPY"}, 0, "", "", true},  // too many currencies
+		{[]string{"1500", "100", "USD", "EUR"}, 0, "", "", true},  // multiple amounts
+		{[]string{"-100", "USD", "EUR"}, 0, "", "", true},         // negative
+	}
+
+	for _, c := range cases {
+		amt, base, quote, err := fxParseConvert(c.in)
+		if c.shouldErr {
+			if err == nil {
+				t.Errorf("%v: expected error, got %v %s/%s", c.in, amt, base, quote)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%v: unexpected error: %v", c.in, err)
+			continue
+		}
+		if amt != c.amt || base != c.base || quote != c.quote {
+			t.Errorf("%v: got %v %s/%s, want %v %s/%s", c.in, amt, base, quote, c.amt, c.base, c.quote)
+		}
+	}
+}
+
+func TestFxAddCommas(t *testing.T) {
+	cases := []struct {
+		v        float64
+		decimals int
+		want     string
+	}{
+		{1500, 2, "1,500.00"},
+		{1500.5, 2, "1,500.50"},
+		{1234567.89, 2, "1,234,567.89"},
+		{100, 2, "100.00"},
+		{0, 2, "0.00"},
+		{232500, 0, "232,500"},
+		{-1500, 2, "-1,500.00"},
+	}
+	for _, c := range cases {
+		got := fxAddCommas(c.v, c.decimals)
+		if got != c.want {
+			t.Errorf("fxAddCommas(%v, %d) = %q, want %q", c.v, c.decimals, got, c.want)
+		}
+	}
+}