Remove LangChain dependency from prompts

Replace langchain_core.PromptTemplate with simple string formatting class to eliminate LangChain dependency completely.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/prompts.py

@@ -1,7 +1,5 @@
 """Prompt templates for OSINT investigation assistant"""
 
-from langchain_core.prompts import PromptTemplate
-
 
 SYSTEM_PROMPT = """You are an OSINT investigation assistant. Your responses must be SHORT and FOCUSED.
 
@@ -44,12 +42,6 @@ Respond with:
 **Notes:** [1-2 sentences explaining why these specific tools]"""
 
 
-INVESTIGATION_PROMPT = PromptTemplate(
-    template=INVESTIGATION_PROMPT_TEMPLATE,
-    input_variables=["query", "context"]
-)
-
-
 FOLLOWUP_PROMPT_TEMPLATE = """You are an expert OSINT investigation assistant continuing a conversation.
 
 CONVERSATION HISTORY:
@@ -64,12 +56,6 @@ RELEVANT OSINT TOOLS FROM DATABASE:
 Based on the conversation history and the user's follow-up question, provide a helpful response. If they're asking for clarification or more details about a specific tool or technique, provide that information. If they're asking a new question, follow the structured investigation methodology format."""
 
 
-FOLLOWUP_PROMPT = PromptTemplate(
-    template=FOLLOWUP_PROMPT_TEMPLATE,
-    input_variables=["chat_history", "query", "context"]
-)
-
-
 TOOL_RECOMMENDATION_TEMPLATE = """Based on this investigation need: {query}
 
 Available tools:
@@ -84,22 +70,46 @@ Recommend the top 3-5 most relevant tools and explain why each is suitable. Form
 """
 
 
-TOOL_RECOMMENDATION_PROMPT = PromptTemplate(
+class SimplePromptTemplate:
+    """Simple prompt template using string formatting"""
+
+    def __init__(self, template: str, input_variables: list):
+        self.template = template
+        self.input_variables = input_variables
+
+    def format(self, **kwargs) -> str:
+        """Format the template with provided variables"""
+        return self.template.format(**kwargs)
+
+
+INVESTIGATION_PROMPT = SimplePromptTemplate(
+    template=INVESTIGATION_PROMPT_TEMPLATE,
+    input_variables=["query", "context"]
+)
+
+
+FOLLOWUP_PROMPT = SimplePromptTemplate(
+    template=FOLLOWUP_PROMPT_TEMPLATE,
+    input_variables=["chat_history", "query", "context"]
+)
+
+
+TOOL_RECOMMENDATION_PROMPT = SimplePromptTemplate(
     template=TOOL_RECOMMENDATION_TEMPLATE,
     input_variables=["query", "context"]
 )
 
 
-def get_investigation_prompt(include_system: bool = True) -> PromptTemplate:
+def get_investigation_prompt(include_system: bool = True) -> SimplePromptTemplate:
     """Get the main investigation prompt template"""
     return INVESTIGATION_PROMPT
 
 
-def get_followup_prompt() -> PromptTemplate:
+def get_followup_prompt() -> SimplePromptTemplate:
     """Get the follow-up conversation prompt template"""
     return FOLLOWUP_PROMPT
 
 
-def get_tool_recommendation_prompt() -> PromptTemplate:
+def get_tool_recommendation_prompt() -> SimplePromptTemplate:
     """Get the tool recommendation prompt template"""
     return TOOL_RECOMMENDATION_PROMPT