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/db/db.go

@@ -73,14 +73,11 @@ func JobCompleted(jobName, dateKey string) bool {
 
 // MarkJobCompleted marks a scheduled job as completed for the given date key.
 func MarkJobCompleted(jobName, dateKey string) {
-	_, err := Get().Exec(
+	Exec("mark job completed",
 		`INSERT INTO daily_prefetch (job_name, date, completed) VALUES (?, ?, 1)
 		 ON CONFLICT(job_name, date) DO UPDATE SET completed = 1`,
 		jobName, dateKey,
 	)
-	if err != nil {
-		slog.Error("mark job completed", "job", jobName, "date", dateKey, "err", err)
-	}
 }
 
 // CacheGet returns cached data for the given key if it exists and is within ttlSeconds.
@@ -100,15 +97,11 @@ func CacheGet(key string, ttlSeconds int) string {
 
 // CacheSet stores data in the generic API cache.
 func CacheSet(key, data string) {
-	d := Get()
-	_, err := d.Exec(
+	Exec("cache set",
 		`INSERT INTO api_cache (cache_key, data, cached_at) VALUES (?, ?, unixepoch())
 		 ON CONFLICT(cache_key) DO UPDATE SET data = ?, cached_at = unixepoch()`,
 		key, data, data,
 	)
-	if err != nil {
-		slog.Error("cache set", "key", key, "err", err)
-	}
 }
 
 // RunMaintenance purges stale data from cache tables, old rate limits,
@@ -152,6 +145,9 @@ func RunMaintenance() {
 
 		// Daily activity older than 1 year
 		{"daily_activity", `DELETE FROM daily_activity WHERE date < ?`, []interface{}{now.AddDate(-1, 0, 0).Format("2006-01-02")}},
+
+		// Forex rates older than 2 years (analysis needs 52 weeks, keep buffer)
+		{"forex_rates", `DELETE FROM forex_rates WHERE date < ?`, []interface{}{now.AddDate(-2, 0, 0).Format("2006-01-02")}},
 	}
 
 	totalDeleted := int64(0)
@@ -176,6 +172,25 @@ func RunMaintenance() {
 	slog.Info("maintenance: complete", "total_purged", totalDeleted)
 }
 
+// Exec runs a write query, logging any error with the given label.
+// Use for fire-and-forget writes where the error doesn't affect control flow.
+func Exec(label, query string, args ...interface{}) {
+	_, err := Get().Exec(query, args...)
+	if err != nil {
+		slog.Error("db: "+label, "err", err)
+	}
+}
+
+// ExecResult runs a write query and returns the result, logging any error.
+// Use when you need RowsAffected() or LastInsertId() but still want auto-logging.
+func ExecResult(label, query string, args ...interface{}) sql.Result {
+	res, err := Get().Exec(query, args...)
+	if err != nil {
+		slog.Error("db: "+label, "err", err)
+	}
+	return res
+}
+
 const schema = `
 -- Users & XP
 CREATE TABLE IF NOT EXISTS users (
@@ -922,6 +937,35 @@ CREATE TABLE IF NOT EXISTS adventure_arena_log (
 	logged_at     DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
 );
 
+CREATE TABLE IF NOT EXISTS adventure_events_log (
+	id           INTEGER PRIMARY KEY AUTOINCREMENT,
+	user_id      TEXT NOT NULL,
+	event_key    TEXT NOT NULL,
+	triggered_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+	expires_at   DATETIME NOT NULL,
+	responded_at DATETIME,
+	gold_awarded INTEGER NOT NULL DEFAULT 0,
+	xp_awarded   INTEGER NOT NULL DEFAULT 0,
+	outcome      TEXT NOT NULL DEFAULT 'pending'
+);
+CREATE INDEX IF NOT EXISTS idx_adv_events_user_outcome ON adventure_events_log(user_id, outcome);
+
+-- Forex
+CREATE TABLE IF NOT EXISTS forex_rates (
+	currency TEXT NOT NULL,
+	date     TEXT NOT NULL,
+	rate     REAL NOT NULL,
+	PRIMARY KEY (currency, date)
+);
+
+CREATE TABLE IF NOT EXISTS forex_alerts (
+	user_id   TEXT NOT NULL,
+	currency  TEXT NOT NULL,
+	threshold REAL NOT NULL,
+	fired_at  INTEGER NOT NULL DEFAULT 0,
+	PRIMARY KEY (user_id, currency, threshold)
+);
+
 `
 
 // SeedSchedulerDefaults inserts default scheduler jobs if they don't exist.