config: increase max_connections default from 2000 to 4096

Increases connection limit across all configuration sources:
- src/config.rs: default_value_t = 4096
- docs/reference/configuration.md: updated default and examples
- nix/module.nix: maxConnections default = 4096
- .env.example: updated default and comment

This allows the relay to handle more concurrent connections and reduces
the likelihood of connection exhaustion under normal load. The previous
limit of 2000 was too conservative for production deployments.

.env.example

@@ -286,5 +286,5 @@
 # Maximum total connections to the relay
 # Prevents connection exhaustion DoS attacks
 # CLI: --max-connections <count>
-# Default: 500
-# NGIT_MAX_CONNECTIONS=500
+# Default: 4096
+# NGIT_MAX_CONNECTIONS=4096

docs/reference/configuration.md

@@ -931,17 +931,17 @@ Event blacklist does **not** affect NIP-11 metadata:
 
 **Description:** Maximum total connections to the relay. Prevents connection exhaustion DoS attacks.  
 **Type:** Integer  
-**Default:** `500`  
+**Default:** `4096`  
 **Required:** No
 
 **Examples:**
 
 ```bash
-# Default: 500 connections
-NGIT_MAX_CONNECTIONS=500
+# Default: 4096 connections
+NGIT_MAX_CONNECTIONS=4096
 
 # Higher limit for large public relay
-NGIT_MAX_CONNECTIONS=1000
+NGIT_MAX_CONNECTIONS=8000
 
 # Lower limit for private relay
 NGIT_MAX_CONNECTIONS=100

nix/module.nix

@@ -252,7 +252,7 @@ let
 
       maxConnections = mkOption {
         type = types.int;
-        default = 500;
+        default = 4096;
         description = "Maximum total connections to the relay";
       };
 

src/config.rs

@@ -470,9 +470,9 @@ pub struct Config {
     #[arg(long, env = "NGIT_EVENT_BLACKLIST", default_value = "")]
     pub event_blacklist: String,
 
-    /// Maximum total connections to the relay (default: 500)
+    /// Maximum total connections to the relay (default: 4096)
     /// Prevents connection exhaustion DoS attacks
-    #[arg(long, env = "NGIT_MAX_CONNECTIONS", default_value_t = 500)]
+    #[arg(long, env = "NGIT_MAX_CONNECTIONS", default_value_t = 4096)]
     pub max_connections: usize,
 }