feat: paste overflow via FlaskPaste for long replies

Add Bot.long_reply() that sends lines directly when under threshold,
or creates a FlaskPaste paste with preview + link when over. Refactor
abuseipdb, alert history, crtsh, dork, exploitdb, and subdomain
plugins to use long_reply(). Configurable paste_threshold (default: 4).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/abuseipdb.py

@@ -142,5 +142,4 @@ async def cmd_abuse(bot, message):
             return f"{addr} -- error: {exc}"
 
     results = await asyncio.gather(*[_query(a) for a in addrs])
-    for line in results:
-        await bot.reply(message, line)
+    await bot.long_reply(message, list(results), label="abuse check")