Detect declined sessions (200 + Status:Error); theme Sessions screen

- startParkingSession: server returns HTTP 200 even on a declined charge — now
  detect Response.Status:"Error" and throw the gateway reason (e.g. "DECLINED")
  so the app shows the failure instead of a false "Parked!"
- Confirmed the session request format is correct (server processed it); expand
  StartParkingSessionResponse with the real fields (OriginalErrorMessage, etc.)
- Theme SessionsScreen (was black-on-black in dark mode)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

parksmarter-client/src/types.ts

@@ -452,8 +452,29 @@ export interface StartParkingSessionParams {
   bleEncBytes?: string;
 }
 
+/**
+ * POST /api/Session. CONFIRMED via live capture. Returns HTTP 200 even on a
+ * declined charge — check `Response.Status === 'Error'` (the client does this and
+ * throws). `OriginalErrorMessage` carries the gateway reason (e.g. "DECLINED").
+ */
 export interface StartParkingSessionResponse {
-  BleEncBytes?: string;
+  Response?: ResponseEnvelope;
+  BleEncBytes?: string | null;
+  PBPParkingSessionId?: number;
+  OriginalErrorMessage?: string;
+  StartTime?: string | null;
+  EndTime?: string | null;
+  TimePurchased?: string | null;
+  ZoneID?: number | string | null;
+  Zone?: string | null;
+  SpaceID?: number | string | null;
+  Space?: string | null;
+  VehicleNumber?: string | null;
+  Lat?: number | null;
+  Long?: number | null;
+  TransactionFee?: string | number | null;
+  Amount?: string | number | null;
+  AmountCharged?: string | number | null;
   [key: string]: unknown;
 }