fix(deploy): remove heredoc from SSH deploy script causing step 6 failure

[Copilot]

The "Deploy to EC2" step was exiting with status 1 immediately after the first echo, traced to a cat > .env << 'ENVEOF' heredoc that both breaks under SSH piped script execution and is dead code (immediately overwritten by the subsequent { } > .env block).

Changes

• Remove heredoc — eliminates cat > .env << 'ENVEOF' ... ENVEOF block; heredoc terminators are unreliable when scripts are transmitted via SSH pipe
• Move header into { } > .env block — preserves the # Auto-generated + timestamp comment as echo statements inside the block that actually writes the file
• Add mkdir -p /opt/quanttrade — defensive guard before cd for fresh-server deployments where SCP may not have pre-created the directory

-            cat > .env << 'ENVEOF'
-            # Auto-generated by GitHub Actions deploy
-            # Last updated: $(date -u +"%Y-%m-%dT%H:%M:%SZ")
-            ENVEOF
-
-            # Write each secret (only if non-empty)
             {
+              echo "# Auto-generated by GitHub Actions deploy"
+              echo "# Last updated: $(date -u +"%Y-%m-%dT%H:%M:%SZ")"
               echo "# === Database ==="

Original prompt

Reference: https://github.com/YashJoshi2109/QuantTrade-AI/actions/runs/22621071007/job/65547152259#step:6:1

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