feat: Telegram digest bot + event-detail improvements + VS Code launch

[ukurere]

Summary

Three features developed in this session, building on top of the earlier admin page, RSS polling, profile tabs, and event-card toggle work:

• Event-detail page — renders full RSS HTML content via DomSanitizer, functional ★ Save and 📅 Calendar toggle buttons (top + bottom bars), complete SCSS overhaul for article body (images, headings, blockquotes, code blocks, links, tables)
• Telegram bot notifications — users enter their @username in the profile, send /start to the bot, and the bot links the account automatically; digests are sent in parallel to email + Telegram; /digest command on demand; NullTelegramBotService stub when token is not configured
• VS Code one-click launch — .vscode/launch.json compound config (🚀 Full Stack) builds the .NET backend with debugger + starts ng serve in a dedicated terminal and opens Chrome, all with a single F5

Changes

Backend

• User model: TelegramUsername, TelegramChatId (long?), TelegramNotificationsEnabled
• EF migration AddTelegramFields
• ITelegramBotService / TelegramBotService (Telegram.Bot 22.x, HTML parse mode, auto-split at 4 000 chars)
• NullTelegramBotService — no-op when Telegram:BotToken is not configured
• TelegramBotBackgroundService — long polling; /start links account by username; /digest sends on-demand
• DigestService.SendDigestAsync — sends Telegram message alongside email when enabled
• DigestService.SendTelegramDigestAsync — Telegram-only path used by /digest command
• UsersController — PATCH /{id}/telegram endpoint; telegram fields exposed in MapUser
• appsettings.example.json — Telegram:BotToken placeholder added

Frontend

• User model — telegramNotificationsEnabled, telegramUsername, telegramChatId
• UsersService.updateTelegram() — PATCH call
• Profile page — mat-slide-toggle to enable/disable, @username input, connection status chip (✅ connected / ⏳ waiting for /start), saveTelegram() method; MatSlideToggleModule added
• Event-detail — [innerHTML]="safeContent()", toggle buttons, full SCSS for article body
• EventItem.contentHtml? field added to model

Dev tooling

• .vscode/tasks.json — build: backend (dotnet build) + serve: frontend (ng serve, background with pattern matcher)
• .vscode/launch.json — compound 🚀 Full Stack (coreclr + chrome), stopAll: true

Test plan

• Open repo in VS Code → press F5 → Angular opens in Chrome, .NET starts with debugger
• Create a bot via @Botfather, add token to appsettings.json, run backend
• In profile: enable Telegram, enter username, save → status shows "⏳ Waiting for /start"
• Send /start to bot in Telegram → status changes to "✅ Connected"
• Send /digest to bot → receives personalized digest
• Open any event → full article body renders, ★ and 📅 buttons work and persist

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