feat(bots): anonConfess + shitpostLeaderboard built-in bots

- ConfessBot: polls for /confess messages, deletes original, reposts anonymous
- LeaderboardBot: daily top-10 message count recap from DB
- BotFunc extended with *sql.DB param for DB-reading bots
- Both types registered in runner + BotManager UI

cmd/server/main.go

@@ -83,6 +83,8 @@ func main() {
 	// Built-in bot runner
 	botRunner := bot.NewRunner(database.DB, hub, logger)
 	botRunner.Register("steamfree", bot.SteamFreeBot)
+	botRunner.Register("confess", bot.ConfessBot)
+	botRunner.Register("leaderboard", bot.LeaderboardBot)
 	go botRunner.StartAll()
 
 	// Giphy client (nil if no API key)