Configure secure backend environment via .env file (#137)

This PR introduces the .env file for backend services, including
Supabase service role key, JWT secret, encryption key, and secure RPC
endpoints for Alchemy, Infura, and Stacks. These variables are critical
for protected data access, token verification, and secure blockchain
interactions.

Author: Adnanmd76

.env

@@ -1,7 +1,21 @@
-NEXT_PUBLIC_DEFAULT_CHAIN=ethereum
-NEXT_PUBLIC_DEFAULT_CHAIN_ID=1
-NEXT_PUBLIC_ETH_RPC=https://mainnet.infura.io/v3/YOUR_ID
-NEXT_PUBLIC_POLYGON_RPC=https://polygon-rpc.com
-NEXT_PUBLIC_BSC_RPC=https://bsc-dataseed.binance.org/
-NEXT_PUBLIC_AVALANCHE_RPC=https://api.avax.network/ext/bc/C/rpc
-NEXT_PUBLIC_FANTOM_RPC=https://rpc.ftm.tools
+# 🔗 Supabase (Secure Access)
+SUPABASE_URL=https://rjeeuvdvqwxlkrmyhqzu.supabase.co
+SUPABASE_SERVICE_ROLE_KEY=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJzdXBhYmFzZSIsInJlZiI6InJqZWV1dmR2cXd4bGtybXlocXp1Iiwicm9sZSI6InNlcnZpY2Vfcm9sZSIsImlhdCI6MTc2MTE4Njg1NSwiZXhwIjoyMDc2NzYyODU1fQ.GLwxwcMTJ9SJWZ2EvutFqBpEdJsrdRVsM5sm2R6dNxA
+
+# 🔐 JWT & Encryption
+REACT_APP_JWT_SECRET=727FEBC71F5E262E8EC318AB179F2
+REACT_APP_ENCRYPTION_KEY=34A675FC169BE3D766AE9982AB425
+
+# 🔗 Alchemy
+REACT_APP_ALCHEMY_RPC=https://eth-mainnet.g.alchemy.com/v2/x_K_2laUYi1hd0u9eD6s_
+
+# 🔗 Infura
+REACT_APP_INFURA_SECRET=iiEytS3KKgQj4yWJ2mp+Qv+S2727ieYdRI901Q614tbS/gXShy3FyQ
+REACT_APP_INFURA_RPC=https://mainnet.infura.io/v3/12b3d0197207427781a02664aee65b0e
+
+# 🌐 Stacks
+REACT_APP_STACKS_API=https://api.platform.hiro.so/v1/ext/4c3a318c42983c1951a4c82e899bbecb/stacks-blockchain-api
+
+# ⚙️ Environment Flags
+NODE_ENV=production
+DEBUG=false