chore(rewrite-v2): add .env.example

Environment template for bot token, database URL, captcha config,
and optional group IDs.

Author: MattiaFailla

.env.example

@@ -0,0 +1,18 @@
+# Required: Bot token from @BotFather
+TELEGRAM_BOT_TOKEN=your_bot_token_here
+
+# Optional: PostgreSQL connection string (Neon or other PostgreSQL)
+# When set, uses PostgresRepository; otherwise uses InMemoryRepository
+# DATABASE_URL=postgresql://user:password@host/neondb?sslmode=require
+
+# Captcha: secret command users must send in DM after reading the rules file
+CAPTCHA_SECRET_COMMAND=python-italy
+
+# Path to the rules/captcha file (relative to project root)
+CAPTCHA_FILE_PATH=assets/regolamento.md
+
+# Optional: Main group ID for multi-group logic
+# MAIN_GROUP_ID=-1001234567890
+
+# Optional: Comma-separated list of local sub-group IDs
+# LOCAL_GROUP_IDS=-1001234567891,-1001234567892