fix(solana): airdrop SOL to mint authority before creating mint

Mint authority had zero SOL balance on devnet, causing
'Attempt to debit an account but found no record of a prior
credit' error. Now getTokenMint() checks balance, airdrops 2 SOL
if needed, then creates the SPL token mint. Also added caching
so mint is only created once.

backend/src/services/solana.ts

@@ -38,22 +38,41 @@ try {
 
 export const connection = new Connection(RPC_URL, "confirmed");
 
+let cachedMint: PublicKey | null = null;
+
 // Get or create token mint address
 export async function getTokenMint(): Promise<PublicKey | null> {
 	try {
-		// Check env first
+		// Return cached mint
-		if (process.env.SOLANA_MINT_ADDRESS) {
+		if (cachedMint) {
-			return new PublicKey(process.env.SOLANA_MINT_ADDRESS);
+			return cachedMint;
 		}
 
-		// Check database
+		// Check env first
-		const config = await prisma.systemSettings.findFirst();
+		if (process.env.SOLANA_MINT_ADDRESS) {
-		if (config?.id) {
+			cachedMint = new PublicKey(process.env.SOLANA_MINT_ADDRESS);
-			// Use a fixed mint derived from program ID for determinism
+			return cachedMint;
-			const mintKeypair = Keypair.generate();
+		}
-			// For now, auto-create mint on devnet if authority exists
+
+		// Auto-create mint on devnet if authority exists
 		if (mintAuthority && RPC_URL.includes("devnet")) {
 			console.log("Auto-creating token mint on devnet...");
+
+			// Fund mint authority with SOL first
+			const balance = await connection.getBalance(mintAuthority.publicKey);
+			if (balance < 500000000) {
+				console.log(
+					`Airdropping SOL to mint authority ${mintAuthority.publicKey.toBase58()}...`,
+				);
+				const signature = await connection.requestAirdrop(
+					mintAuthority.publicKey,
+					2 * 1000000000,
+				);
+				await connection.confirmTransaction(signature);
+				console.log("Airdrop complete");
+			}
+
+			const mintKeypair = Keypair.generate();
 			const mint = await createMint(
 				connection,
 				mintAuthority,
@@ -62,10 +81,13 @@ export async function getTokenMint(): Promise<PublicKey | null> {
 				DECIMALS,
 				mintKeypair,
 			);
+			cachedMint = mint;
 			console.log(`Token mint created: ${mint.toBase58()}`);
+			console.log(
+				`Add SOLANA_MINT_ADDRESS=${mint.toBase58()} to your .env to persist it`,
+			);
 			return mint;
 		}
-		}
 		return null;
 	} catch (error) {
 		console.error("Failed to get token mint:", error);