Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

server/internal/api/config_handler_test.go

@@ -10,8 +10,6 @@ import (
 	"net/http/httptest"
 	"strings"
 	"testing"
-
-	"crypto-miner-server/internal/db"
 )
 
 // stubConfigProvider implements ConfigProvider for handler unit tests.
@@ -39,17 +37,12 @@ func (s *stubConfigProvider) UpdateConfigFromJSON(data json.RawMessage) error {
 
 func newTestConfigHandler(t *testing.T, cp ConfigProvider) *ConfigHandler {
 	t.Helper()
-	database, err := db.New(t.TempDir())
-	if err != nil {
-		t.Fatal(err)
-	}
-	t.Cleanup(func() { database.Close() })
-	return NewConfigHandler(database, cp)
+	return NewConfigHandler(cp)
 }
 
 func TestNewConfigHandler(t *testing.T) {
 	h := newTestConfigHandler(t, &stubConfigProvider{})
-	if h == nil || h.config == nil || h.db == nil {
+	if h == nil || h.config == nil {
 		t.Fatal("NewConfigHandler returned incomplete handler")
 	}
 }