refactor: db-only credits and admin controls

Remove blockchain dependence from credit flow:
- watch credits now DB-only
- webhook earnings now DB-only
- wallet balance now DB-only
- admin bonus/adjustment routes operate on DB totals

Add admin adjustment API for account control.
Keep Solana service file unused for now; safe to delete later.

backend/src/routes/auth.ts

@@ -3,7 +3,7 @@ import crypto from "crypto";
 import { Router } from "express";
 import jwt from "jsonwebtoken";
 import { asyncHandler } from "../middleware/errorHandler";
-import { createWallet, mintTokens } from "../services/solana";
+import { createWallet } from "../services/solana";
 import { prisma } from "../utils/prisma";
 
 const ENCRYPTION_KEY =
@@ -374,31 +374,21 @@ async function backfillUserHistory(user: {
 				},
 			});
 
-			// Mint tokens on Solana
-			const signature = await mintTokens(user.walletAddress!, creditsEarned, {
-				sessionId,
-				contentTitle: item.title || item.full_title || "Unknown",
-				watchDurationMinutes,
+			// DB-only credit record
+			await prisma.transaction.create({
+				data: {
+					userId: user.id,
+					type: "EARN",
+					amount: creditsEarned,
+					watchEventId: watchEvent.id,
+					description: `Watched ${item.title || item.full_title || "Unknown"}`,
+					contentTitle: item.title || item.full_title || "Unknown",
+				},
 			});
 
-			if (signature) {
-				// Create transaction record
-				await prisma.transaction.create({
-					data: {
-						userId: user.id,
-						type: "EARN",
-						amount: creditsEarned,
-						watchEventId: watchEvent.id,
-						solanaSignature: signature,
-						description: `Watched ${item.title || item.full_title || "Unknown"}`,
-						contentTitle: item.title || item.full_title || "Unknown",
-					},
-				});
-
-				totalCredits += creditsEarned;
-				totalMinutes += watchDurationMinutes;
-				processedCount++;
-			}
+			totalCredits += creditsEarned;
+			totalMinutes += watchDurationMinutes;
+			processedCount++;
 		}
 
 		// Update user stats