chore(mcp): remove unused database timeout config (#2975)

Why this change was needed:
The mcp-proxy database timeout setting is defined in config and shown in the sample config, but the database initialization path does not read it. Keeping it suggests a configurable behavior that does not exist.

What changed:
Removed the unused Database.Timeout field and the matching timeout entry from the mcp-proxy config template.

Problem solved:
The database config surface no longer exposes a dead timeout option.

Author: wklken

src/mcp-proxy/config.yaml.tpl

@@ -24,7 +24,6 @@ databases:
     maxOpenConns: 200
     maxIdleConns: 50
     connMaxLifetimeSecond: 600
-    timeout: 2
     # TLS配置（可选）
     tls:
       enabled: false

src/mcp-proxy/pkg/config/config.go

@@ -102,8 +102,6 @@ type Database struct {
 	MaxOpenConns          int
 	MaxIdleConns          int
 	ConnMaxLifetimeSecond int
-	// connect: s
-	Timeout int
 	// tls
 	TLS TLS
 }