feat: add wave 1 plugins (dns, encode, hash, defang, revshell, cidr)

All pure stdlib, zero external dependencies:
- dns: raw UDP resolver with A/AAAA/MX/NS/TXT/CNAME/PTR/SOA
- encode: base64, hex, URL, ROT13 encode/decode
- hash: md5/sha1/sha256/sha512 generation + type identification
- defang: IOC defanging/refanging for safe sharing
- revshell: reverse shell one-liners for 11 languages
- cidr: subnet calculator with IP membership check

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

plugins/encode.py

@@ -0,0 +1,75 @@
+"""Plugin: encode and decode strings (base64, hex, URL, ROT13)."""
+
+from __future__ import annotations
+
+import base64
+import urllib.parse
+
+from derp.plugin import command
+
+_ROT13 = str.maketrans(
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
+    "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm",
+)
+
+_ENCODERS: dict[str, tuple[str, callable]] = {
+    "b64": ("Base64", lambda t: base64.b64encode(t.encode()).decode()),
+    "hex": ("Hex", lambda t: t.encode().hex()),
+    "url": ("URL", lambda t: urllib.parse.quote(t, safe="")),
+    "rot13": ("ROT13", lambda t: t.translate(_ROT13)),
+}
+
+_DECODERS: dict[str, tuple[str, callable]] = {
+    "b64": ("Base64", lambda t: base64.b64decode(t).decode("utf-8", errors="replace")),
+    "hex": ("Hex", lambda t: bytes.fromhex(t).decode("utf-8", errors="replace")),
+    "url": ("URL", lambda t: urllib.parse.unquote(t)),
+    "rot13": ("ROT13", lambda t: t.translate(_ROT13)),
+}
+
+_FORMATS = ", ".join(_ENCODERS)
+
+
+@command("encode", help=f"Encode text: !encode <{_FORMATS}> <text>")
+async def cmd_encode(bot, message):
+    """Encode text in the specified format."""
+    parts = message.text.split(None, 2)
+    if len(parts) < 3:
+        await bot.reply(message, f"Usage: !encode <{_FORMATS}> <text>")
+        return
+
+    fmt = parts[1].lower()
+    text = parts[2]
+
+    entry = _ENCODERS.get(fmt)
+    if entry is None:
+        await bot.reply(message, f"Unknown format: {fmt} (valid: {_FORMATS})")
+        return
+
+    try:
+        result = entry[1](text)
+        await bot.reply(message, result)
+    except Exception as exc:
+        await bot.reply(message, f"Encode error: {exc}")
+
+
+@command("decode", help=f"Decode text: !decode <{_FORMATS}> <text>")
+async def cmd_decode(bot, message):
+    """Decode text from the specified format."""
+    parts = message.text.split(None, 2)
+    if len(parts) < 3:
+        await bot.reply(message, f"Usage: !decode <{_FORMATS}> <text>")
+        return
+
+    fmt = parts[1].lower()
+    text = parts[2]
+
+    entry = _DECODERS.get(fmt)
+    if entry is None:
+        await bot.reply(message, f"Unknown format: {fmt} (valid: {_FORMATS})")
+        return
+
+    try:
+        result = entry[1](text)
+        await bot.reply(message, result)
+    except Exception as exc:
+        await bot.reply(message, f"Decode error: {exc}")