feat: add !paste command and unit tests for 5 core plugins

Add cmd_paste to flaskpaste plugin (create paste, return URL).
Add test suites for encode, hash, defang, cidr, and dns plugins
(83 new test cases, 1093 total).

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

plugins/flaskpaste.py

@@ -192,3 +192,33 @@ async def cmd_shorten(bot, message):
         await bot.reply(message, short)
     else:
         await bot.reply(message, "shorten failed: no URL returned")
+
+
+@command("paste", help="Create a paste: !paste <text>")
+async def cmd_paste(bot, message):
+    """Create a paste via FlaskPaste.
+
+    Usage:
+        !paste some text to paste
+    """
+    parts = message.text.split(None, 1)
+    if len(parts) < 2:
+        await bot.reply(message, "Usage: !paste <text>")
+        return
+
+    content = parts[1]
+    base_url = _get_base_url(bot)
+    loop = asyncio.get_running_loop()
+
+    try:
+        url = await loop.run_in_executor(
+            None, _create_paste, base_url, content,
+        )
+    except Exception as exc:
+        await bot.reply(message, f"paste failed: {exc}")
+        return
+
+    if url:
+        await bot.reply(message, url)
+    else:
+        await bot.reply(message, "paste failed: no URL returned")