fix: 2026-06-04 audit pass — README, USB pack, multi-area fixes

WS ticket dashboard auth, builder universal signing/size limits/fusion obfuscation/dropper bundles, Path Tracer WireGuard topology, SessionGate degraded mode and download timeouts, server bootstrap (data dir, cloudflared dedupe, config port precedence), agent mesh/miner/spread fixes. README refreshed; usb bundle repacked; PROBLEMS.md audit log updated.

server/internal/db/sqlite.go

@@ -20,8 +20,9 @@ type Database struct {
 func New(dataDir string) (*Database, error) {
 	dbPath := filepath.Join(dataDir, "miner.db")
 
-	// Ensure directory exists
-	os.MkdirAll(filepath.Dir(dbPath), 0755)
+	if err := os.MkdirAll(filepath.Dir(dbPath), 0755); err != nil {
+		return nil, fmt.Errorf("create data directory: %w", err)
+	}
 
 	db, err := sql.Open("sqlite", dbPath+"?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)")
 	if err != nil {