feat(bot): refactor system prompt and enhance CLI command

- Replaced `DEFAULT_SYSTEM_PROMPT` with `BOT_SYSTEM_PROMPT` for clarity and modularity.
- Introduced a `build_system_prompt` function to dynamically compose prompts.
- Enhanced `call_claude` CLI with new tool options and appendable prompts.

systems/x86_64-linux/mx/nextcloud-claude-bot/bot.py

@@ -101,7 +101,8 @@ def verify_signature(body: bytes, signature: str, random: Optional[str] = None)
     return False
 
 
-DEFAULT_SYSTEM_PROMPT = """Du bist Claude, ein KI-Assistent im Nextcloud Talk Chat.
+BOT_SYSTEM_PROMPT = """\
+Du bist ein KI-Assistent im Nextcloud Talk Chat.
 Deine Antworten werden direkt in den Chatraum gepostet.
 Halte deine Antworten kurz und prägnant, da es ein Chat ist.
 Nutze Markdown für Formatierung wenn sinnvoll.
@@ -111,18 +112,16 @@ Du erhältst:
 - <current_message>: Die aktuelle Nachricht, auf die du antworten sollst"""
 
 
-def build_prompt(conversation_token: str, current_message: str, current_user: str) -> str:
-    """Build prompt with in-memory conversation history using XML structure."""
-    parts = []
-
-    # Add system prompt (hardcoded + optional custom)
-    parts.append("<system>")
-    parts.append(DEFAULT_SYSTEM_PROMPT)
+def build_system_prompt() -> str:
+    """Build the full system prompt from hardcoded + optional custom parts."""
     if SYSTEM_PROMPT:
-        parts.append("")
-        parts.append(SYSTEM_PROMPT.strip())
-    parts.append("</system>")
-    parts.append("")
+        return f"{BOT_SYSTEM_PROMPT}\n\n{SYSTEM_PROMPT.strip()}"
+    return BOT_SYSTEM_PROMPT
+
+
+def build_prompt(conversation_token: str, current_message: str, current_user: str) -> str:
+    """Build user prompt with in-memory conversation history using XML structure."""
+    parts = []
 
     # Add chat history if available
     history = conversations.get(conversation_token, [])
@@ -143,9 +142,14 @@ def build_prompt(conversation_token: str, current_message: str, current_user: st
 
 async def call_claude(prompt: str) -> str:
     """Call Claude CLI and return response."""
-    cmd = [CLAUDE_PATH, "--print"]
+    cmd = [
+        CLAUDE_PATH, "--print",
+        "--tools", "WebSearch,WebFetch",
+        "--allowedTools", "WebSearch,WebFetch",
+        "--append-system-prompt", build_system_prompt(),
+    ]
 
-    log.info(f"Calling Claude: {' '.join(cmd)}")
+    log.info(f"Calling Claude: {cmd[0]} --print --append-system-prompt ...")
     
     try:
         proc = await asyncio.create_subprocess_exec(