add tag all function

CLAUDE.md

@@ -41,6 +41,25 @@ The bot ignores messages from chats not in this list.
 - `src/handlers/` - Message handlers (modular, each feature in own file)
 - `src/utils/` - Shared utilities
 
+## NixOS Deployment
+
+Module location: `/home/fabian/nix/sys/modules/task-force-beta-bot.nix`
+
+```nix
+local.sys.task-force-beta-bot = {
+  enable = true;
+  tokenFile = "/var/trust/task_force_beta_bot/telegram_token";
+  allowedChats = [ (-1001234567890) ];  # Negative IDs for groups
+};
+```
+
+The module:
+- Fetches and builds the package from git
+- Generates the allowed chats file in the nix store
+- Runs as a hardened systemd service (`task-force-beta-bot.service`)
+
+After code changes: update `rev` and `hash` in the module's `fetchgit` block.
+
 ## Adding New Handlers
 
 1. Create `src/handlers/new_feature.rs`
@@ -57,3 +76,11 @@ Strips tracking parameters from Instagram links:
 - `ref` - Referral tracking
 - `fbclid` - Facebook click ID
 - `si` - Session identifier
+
+### Tag All (`handlers/tag_all.rs`)
+
+WhatsApp-style @all mentions. When a message contains "@all", bot replies tagging everyone it has seen.
+
+- Tracks users by observing messages (requires privacy mode disabled)
+- In-memory only - resets on restart
+- Uses MarkdownV2 text mentions