v0.2.3 - Moderation, Embeds & UI Overhaul

Features

Added server roles: Owner, Admin, Mod, Member — first registered user is automatically Owner
New /kick, /ban, /unban, /mute, /unmute, /role, /nuke commands for moderators and admins
ModerationController with full REST API for role assignment, kicks, bans, mutes, message deletion, and channel nuking
Mutes support optional duration (auto-expire) and blocked users cannot log in
Role claim included in JWT tokens; role badges shown in the online users panel

Channels can be created as public or private via a checkbox in the Create Channel dialog
Public channels are visible to all users; private channels only appear for members who joined them
Persistent channel membership tracked in the database (ChannelMembership table)
GET /api/channels returns the combined list: public channels + user's joined private channels
Channel creators are automatically added as members

Messages containing URLs now show a rich preview below the message text
Server-side fetching: detects the first URL in a message, fetches the page, and parses OpenGraph meta tags (og:title, og:description, og:image, og:site_name)
OG images are converted to a small 24x12 colored ASCII thumbnail using the existing half-block renderer
Embeds are persisted in the database and included in channel history
TUI client renders embeds with a ▏ left border bar — site name and border in blue, title in white, description in gray, followed by the ASCII thumbnail
IRC gateway receives a text-only embed preview (site name, title, description) — no ASCII thumbnail to keep IRC output clean
Falls back to <title> tag when no OG tags are present; gracefully skips if no useful metadata is found
3-second fetch timeout ensures message delivery is never significantly delayed
SSRF protection rejects private/loopback IP addresses before fetching

Collapsible right-side panel showing online users in the current channel (toggle with F2)
Users displayed with status indicators, role badges, and their custom nickname colors
Panel updates on join, leave, and status change events

Half-block character rendering (▀/█) with separate foreground + background colors for 2x vertical resolution
Switched from ANSI escape codes to printable color tags ({F:RRGGBB}, {B:RRGGBB}, {X}) — no control bytes in stored content
Optional size parameter for /send command: -s (40x40), -m (80x80, default), -l (120x120)
IRC gateway converts color tags back to ANSI for IRC client compatibility

Version number shown in the status bar
Custom colored rendering for channel list (active indicator, unread count badges)
Avatar upload field added to the profile edit dialog (file path or URL)
Profile avatar now renders with full color tag support in the profile view dialog
Update check notification on connect — shows a system message if a newer GitHub release exists
Chat messages no longer show selection/focus highlight
Exit shortcut changed from Ctrl+C to Alt+Q — frees Ctrl+C for copy
Default history increased from 50 to 100 messages on channel join

Fixed #general channel not visible after adding the IsPublic column — migration default changed to true and startup service ensures it
Fixed channels disappearing when creating a new channel — replaced full re-fetch with incremental updates
Wired OnChannelUpdated SignalR event so new public channels appear for all connected users in real time
Fixed color tag parser using wrong regex group numbers (6,7,8 instead of 1,2,3) — new ASCII art was rendering without colors
Full Unicode/emoji support — renderers use Terminal.Gui v2 grapheme cluster API (GraphemeHelper, AddStr) for proper wide character handling
Emoji-to-text shortcode conversion for consistent cross-platform rendering
Fixed /send and /avatar commands not handling file paths with spaces correctly, even when quoted
Server-side newline spam protection — consecutive blank/whitespace-only lines collapsed to 1 and total lines capped at 30

New LinkEmbedService on the server — URL detection, HTML fetching (first 64KB), OG tag parsing via regex, image thumbnail generation
EmbedDto record added to shared Core DTOs; MessageDto extended with optional Embed field (backward-compatible)
EmbedJson nullable column on the Message table stores serialized embed data (max 8KB)
Dedicated "OgFetch" named HttpClient with bot User-Agent header and 5-second timeout
NotificationSoundService for cross-platform audio playback of embedded notification sounds
Startup DataMigrationService automatically converts old ANSI-format messages to the new color tag format on server boot, logging the count of migrated records
EmojiHelper utility for emoji-to-shortcode conversion
Heartbeat handling in ServerDirectoryService for connection health checks
Four new EF Core migrations: AddModerationRoles, AddChannelIsPublic, AddChannelMembership, AddMessageEmbed
ChannelMembership table with cascade delete on both channel and user removal