v3.0.0: User metrics, expanded type labels, legacy metric removal (#9)

Added

• User metrics: dispatcharr_user_info, dispatcharr_user_date_joined_timestamp, dispatcharr_user_stream_limit, and dispatcharr_user_active_streams (opt-in via new Include User Statistics setting)
• dispatcharr_m3u_account_info gauge providing metadata for each M3U account
• Per-type breakdown on dispatcharr_active_streams with type="live" and type="vod" labels
• type label added to dispatcharr_stream_fps, dispatcharr_stream_video_bitrate_bps, dispatcharr_stream_transcode_bitrate_bps, dispatcharr_stream_current_bitrate_bps, dispatcharr_stream_channel_number, dispatcharr_stream_index, and dispatcharr_stream_available_streams
• user_id and username labels on dispatcharr_client_info
• Manual stop flag - stopping the server now prevents auto-start from restarting it until explicitly started again

Changed

• Minimum Dispatcharr version raised to v0.22.0
• "Start Server" and "Restart Server" action buttons merged into a single "Start / Restart Metrics Server" button

Removed

• Legacy metrics (dispatcharr_stream_info, legacy dispatcharr_m3u_account_info with stream_count label, legacy dispatcharr_epg_source_info with priority label) and the Include Legacy Metric Formats setting
• Disable Update Notifications setting and the Check for Updates action button