explorer/site: add support for explorer nodes running on multiple networks (localnet, testnet, mainnet)

This update introduces configuration support for multiple networks (localnet, testnet, and mainnet) in the explorer site, enabling tailored provisioning for development, testing, and production environments.

Summary of Updates:
- Added network-specific configurations in `site_config.toml` based on the latest `explorerd` configurations
- Set up `log_path` directories for each network
- Removed devnet placeholder configuration

bin/explorer/site/site_config.toml

@@ -19,22 +19,16 @@
 [localnet]
 explorer_rpc_url = "127.0.0.1"
 explorer_rpc_port = 14567
-log_path = "."
+log_path = "~/.local/share/darkfi/explorer_site/localnet"
 
-# devnet configuration
-[devnet]
-explorer_rpc_url = "TODO"
-explorer_rpc_port = "TODO"
-log_path = "TODO"
-
-# testnet configuration
+# Testnet configuration
 [testnet]
-explorer_rpc_url = "TODO"
-explorer_rpc_port = "TODO"
-log_path = "TODO"
+explorer_rpc_url = "127.0.0.1"
+explorer_rpc_port = 14667
+log_path = "~/.local/share/darkfi/explorer_site/testnet"
 
-# mainnet configuration
+# Mainnet configuration
 [mainnet]
-explorer_rpc_url = "TODO"
-explorer_rpc_port = "TODO"
-log_path = "TODO"
+explorer_rpc_url = "127.0.0.1"
+explorer_rpc_port = 14767
+log_path = "~/.local/share/darkfi/explorer_site/mainnet"