Full codebase audit: 21 security/robustness fixes, 328 tests across 4 packages

Security & economy:
- Credit()/Debit() reject non-positive amounts (closes infinite-money exploit)
- Lottery ticket purchase uses in-transaction count check (closes TOCTOU race)
- Arena bail channel ownership prevents double-close panic
- Entry.ID validated before exec.Command in fetch-esteemed
- Internal errors no longer leaked to users (forex, esteemed)

Robustness:
- safeGo() panic recovery added to 17 goroutine launch sites across 14 plugins
- db.Close() added and called on shutdown
- Miniflux mutex pattern fixed (snapshot-under-lock)
- Silently ignored DB/JSON errors now logged (lottery_db)

Performance:
- Added indexes: idx_arena_runs_user(user_id, status), idx_euro_bal_user(user_id)

UX:
- Empty !buy args shows usage instead of "No item matching ''"
- "Failed to load character" now suggests !adventure

Test coverage:
- internal/util/parser_test.go (19 tests: XP, levels, progress bar, commands, parsing)
- internal/crypto/crypto_test.go (12 tests: encrypt/decrypt, HMAC, ParseKey)
- internal/plugin/helpers_test.go (30 tests: formatNumber, calc, lottery, chat perks)
- internal/plugin/audit_fixes_test.go (25 tests: safeGo, bail channels, error leaks, overflow)
- internal/db/db_test.go (4 tests: Init, Close, schema indexes)

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

cmd/fetch-esteemed/main.go

@@ -85,6 +85,12 @@ func main() {
 	failed := 0
 
 	for i, entry := range entries {
+		// Validate entry ID to prevent path traversal or command injection.
+		if entry.ID == "" || strings.ContainsAny(entry.ID, "/\\;|&$`\"'") || strings.Contains(entry.ID, "..") {
+			fmt.Printf("[%d/%d] SKIP (invalid ID): %q\n", i+1, len(entries), entry.ID)
+			skipped++
+			continue
+		}
 		outPath := filepath.Join(outputDir, entry.ID+".jpg")
 
 		// Skip if already downloaded