feat: Add JWT authentication and API key security

- Add users table for dashboard authentication (email, password_hash, role)
- Add api_keys table for agent authentication (key_hash, prefix, name)
- Implement JWT auth with 24h expiration
- Implement API key auth with SHA256 hashing
- Add auth endpoints: POST /api/v1/auth/login, POST /api/v1/auth/register
- Add API key endpoints: GET/POST/DELETE /api/v1/api-keys
- Protect all /api/v1/* routes (except /health and /auth/*)
- Create default admin user (admin@ophion.local)
- First registered user automatically becomes admin
- Use bcrypt for password hashing (cost 12)
- Use SHA256 for API key hashing
- Add security headers middleware

internal/ai/insights.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"time"
 )
 
 // InsightsEngine motor de geração de insights