[TODO] Create models for MongoDB

Add these models,

/src/models/Stream.js
Stores: title, category, tags, streamerId, isLive
chatDisabled, viewerCount, thumbnail, createdAt

/src/models/ModerationAction.js
Stores: moderatorId, targetUserId, actionType (mute, ban, timeout, promote, etc.), duration (for timeout), reason, timestamp

/src/models/ChatMessage.js
Stores: userId, streamId, message, timestamp, deleted (for mod actions)

/src/models/RoleChange.js
Stores: userId, oldRole, newRole, changedBy, timestamp

/src/models/Ban.js
Stores: userId, streamId, reason, bannedBy, expiresAt

/src/models/Timeout.js
Stores: userId, streamId, expiresAt, reason, moderatorId