Add forex plugin, stability fixes, and async HTTP dispatch

- Add forex plugin (Frankfurter v2 API) with rate lookups, analysis,
  DM-based alerts, and daily cron poll. Backfills 1 year of history
  on startup for moving averages and buy signal scoring.

- Fix bot hang caused by SQLite lock contention in reminder polling:
  rows cursor was held open while writing to the same DB. Collect
  results first, close cursor, then process. Same fix in milkcarton.

- Add sync retry loop so the bot reconnects after network drops
  instead of silently exiting. StopSync() for clean Ctrl+C shutdown.

- Add panic recovery to all dispatch, syncer, and cron paths.

- Make all HTTP-calling plugin commands async (goroutines) so a slow
  or dead external API cannot block the message dispatch pipeline.
  Affects: lookup, stocks, forex, anime, movies, concerts, gaming,
  retro, wotd, urls, howami.

- Extract DisplayName to Base, add db.Exec helper, convert silent
  error discards across the codebase.

- Fix UNO mercy-kill bug (eliminated bot continues playing), adventure
  DM nag spam, stats column mismatch, per-call regex/replacer allocs.

- Update README: forex commands, Finance section, 47 plugins.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/plugin/blackjack_test.go

@@ -0,0 +1,88 @@
+package plugin
+
+import "testing"
+
+func TestHandValue_SimpleHand(t *testing.T) {
+	cards := []card{{Rank: 10, Suit: spades}, {Rank: 7, Suit: hearts}}
+	val, soft := handValue(cards)
+	if val != 17 || soft {
+		t.Errorf("got %d soft=%v, want 17 soft=false", val, soft)
+	}
+}
+
+func TestHandValue_AceAsSoft(t *testing.T) {
+	cards := []card{{Rank: 1, Suit: spades}, {Rank: 6, Suit: hearts}}
+	val, soft := handValue(cards)
+	if val != 17 || !soft {
+		t.Errorf("got %d soft=%v, want 17 soft=true", val, soft)
+	}
+}
+
+func TestHandValue_AceDowngradesToOne(t *testing.T) {
+	cards := []card{
+		{Rank: 1, Suit: spades},
+		{Rank: 9, Suit: hearts},
+		{Rank: 5, Suit: diamonds},
+	}
+	val, soft := handValue(cards)
+	// A(11)+9+5 = 25, bust, so A=1: 1+9+5 = 15
+	if val != 15 || soft {
+		t.Errorf("got %d soft=%v, want 15 soft=false", val, soft)
+	}
+}
+
+func TestHandValue_TwoAces(t *testing.T) {
+	cards := []card{
+		{Rank: 1, Suit: spades},
+		{Rank: 1, Suit: hearts},
+	}
+	val, soft := handValue(cards)
+	// A(11)+A(11) = 22, one A->1: 12, still soft
+	if val != 12 || !soft {
+		t.Errorf("got %d soft=%v, want 12 soft=true", val, soft)
+	}
+}
+
+func TestHandValue_FaceCards(t *testing.T) {
+	cards := []card{{Rank: 11, Suit: spades}, {Rank: 12, Suit: hearts}} // J + Q
+	val, soft := handValue(cards)
+	if val != 20 || soft {
+		t.Errorf("got %d soft=%v, want 20 soft=false", val, soft)
+	}
+}
+
+func TestHandValue_Bust(t *testing.T) {
+	cards := []card{
+		{Rank: 10, Suit: spades},
+		{Rank: 8, Suit: hearts},
+		{Rank: 5, Suit: diamonds},
+	}
+	val, _ := handValue(cards)
+	if val != 23 {
+		t.Errorf("got %d, want 23 (bust)", val)
+	}
+}
+
+func TestIsBlackjack(t *testing.T) {
+	tests := []struct {
+		name  string
+		cards []card
+		want  bool
+	}{
+		{"ace+king", []card{{1, spades}, {13, hearts}}, true},
+		{"ace+ten", []card{{1, spades}, {10, hearts}}, true},
+		{"ace+queen", []card{{1, spades}, {12, hearts}}, true},
+		{"ten+jack", []card{{10, spades}, {11, hearts}}, false}, // 20, not 21
+		{"three cards summing 21", []card{{7, spades}, {7, hearts}, {7, diamonds}}, false},
+		{"ace+five", []card{{1, spades}, {5, hearts}}, false}, // 16
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isBlackjack(tt.cards)
+			if got != tt.want {
+				t.Errorf("isBlackjack(%v) = %v, want %v", tt.cards, got, tt.want)
+			}
+		})
+	}
+}