fix: faulty logic when handling environment variable config

[aelxxs]

Corrects logic for loading various fields from environment variables in the configuration loader.

Previously, some fields (e.g. Presence, Shard Count)—were only set when JSON unmarshalling or parsing failed, causing valid configuration values to be ignored.

err := json.Unmarshal([]byte(v), &presence)

// Before
if err != nil { // ← WRONG: Set when invalid
	c.Presence = presence
}

// After
if err == nil { // ← CORRECT: Set when valid
	c.Presence = presence
}

Affected Fields:

• DISCORD_PRESENCE,
• DISCORD_SHARD_IDS
• Numeric Fields: DISCORD_RAW_INTENTS, DISCORD_GATEWAY_VERSION, etc.