Add tarot readings, encrypted quote wall, display name resolution, and uptime reporting

New features:
- !tarot and !tarotspread commands with LLM-powered readings (zodiac-aware)
- !quote system with AES-256-GCM encryption at rest, reply-to-save, search, and quoteboard
- Shared crypto utility (internal/crypto) for AES-256-GCM encrypt/decrypt/HMAC
- ResolveUser now matches display names via room membership as fallback
- !vibe and !tldr show bot uptime when insufficient messages buffered

Bug fixes:
- Fix duplicate quotes table schema that would crash quotewall at runtime
- Fix biased random selection in quote retrieval (use rand.Intn)
- Fix XP rank calculation to handle tied scores with COUNT(DISTINCT xp)
- Scope all leaderboards to room members (repboard, pottyboard, insultboard, firstboard, rankings, emojiboard)

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

main.go

@@ -104,6 +104,8 @@ func main() {
 
 	// Community
 	registry.Register(plugin.NewMilkCartonPlugin(client, ratePlugin))
+	registry.Register(plugin.NewQuoteWallPlugin(client, ratePlugin))
+	registry.Register(plugin.NewTarotPlugin(client, ratePlugin))
 
 	// Tracking (passive)
 	registry.Register(plugin.NewAchievementsPlugin(client, registry))