[CONFIG] Implement Configuration Management with Viper

[fentz26]

Problem

No unified configuration management:

• Hardcoded values
• No environment variable support
• No config file parsing

Proposed Solution

Viper Integration

import "github.com/spf13/viper"

func initConfig() {
    viper.SetConfigName("neona")
    viper.SetConfigType("yaml")
    viper.AddConfigPath("$HOME/.neona")
    viper.AddConfigPath(".")
    
    viper.SetEnvPrefix("NEONA")
    viper.AutomaticEnv()
    
    // Defaults
    viper.SetDefault("server.port", 7466)
    viper.SetDefault("server.host", "127.0.0.1")
    viper.SetDefault("database.path", "~/.neona/neona.db")
    
    viper.ReadInConfig()
}

// Usage
port := viper.GetInt("server.port")

Configuration Sources (Priority Order)

1. Command-line flags
2. Environment variables (NEONA_*)
3. Config file (~/.neona/neona.yaml)
4. Default values

Example Config File

server:
  host: 127.0.0.1
  port: 7466

database:
  path: ~/.neona/neona.db
  
logging:
  level: info
  format: json
  
scheduler:
  max_workers: 10
  poll_interval: 1s
  
connectors:
  claude-cli:
    enabled: true
    timeout: 5m

Acceptance Criteria

• Viper integrated
• Config file support (YAML, JSON, TOML)
• Environment variable support
• Flag overrides
• Configuration validation
• Hot reload option

References

• Parent Epic: 📊 Epic: Observability & Configuration #78