feat: AI agent knows material library — list_materials tool with alias search

Added list_materials tool to the chat agent:
- Searches SCHAEFFLER library materials by name, description, or alias
- Returns material name + schaeffler_code + aliases
- Enables: "zeig mir ein Bild mit Durotect-Material" → agent searches
  for "durotect" → finds SCHAEFFLER_020101_Durotect-Blue → uses as
  material_override

System prompt updated with rules 10-11:
- Explains alias → library material mapping
- Always use full SCHAEFFLER name for material_override

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/chat_service.py

@@ -38,7 +38,9 @@ RULES:
 6. Combine multiple steps into one action. If creating an order, also submit and dispatch it automatically.
 7. Respond in the same language the user writes in.
 8. Be concise — short answers are better than long ones.
-9. When the user says "beliebig", "any", "random", "irgendein" — just pick one yourself, don't ask back."""
+9. When the user says "beliebig", "any", "random", "irgendein" — just pick one yourself, don't ask back.
+10. Material system: Materials have SCHAEFFLER library names (e.g. SCHAEFFLER_020101_Durotect-Blue). Common names like "Durotect", "Stahl", "Bronze" are aliases that map to these library names. When the user asks for a material by a common name, use list_materials to find the correct SCHAEFFLER name, then use that for material_override.
+11. When setting material_override, always use the full SCHAEFFLER library name (e.g. SCHAEFFLER_020101_Durotect-Blue), never the alias."""
 
 # ── Tool definitions (OpenAI function-calling schema) ────────────────────────
 
@@ -241,6 +243,23 @@ TOOLS = [
             },
         },
     },
+    {
+        "type": "function",
+        "function": {
+            "name": "list_materials",
+            "description": "List available SCHAEFFLER library materials with their aliases. Use this to find the correct material name for material_override. Materials have names like SCHAEFFLER_010101_Steel-Bare. Aliases map common names (Stahl, Bronze, Durotect, etc.) to these library materials. When user asks for a material by a common name, search aliases to find the correct SCHAEFFLER library material name.",
+            "parameters": {
+                "type": "object",
+                "properties": {
+                    "query": {
+                        "type": "string",
+                        "description": "Search term to filter materials by name or alias (e.g. 'durotect', 'steel', 'bronze'). Empty for all.",
+                        "default": "",
+                    },
+                },
+            },
+        },
+    },
     {
         "type": "function",
         "function": {
@@ -323,6 +342,8 @@ async def _execute_tool(
             return await _tool_get_render_stats(db, tenant_id)
         elif name == "check_materials":
             return await _tool_check_materials(db, tenant_id, user_id, **arguments)
+        elif name == "list_materials":
+            return await _tool_list_materials(db, tenant_id, **arguments)
         elif name == "find_product_renders":
             return await _tool_find_product_renders(db, tenant_id, **arguments)
         elif name == "query_database":
@@ -634,6 +655,47 @@ async def _tool_check_materials(db: AsyncSession, tenant_id: str, user_id: str =
         return json.dumps({"error": f"Failed to check materials: {exc}"})
 
 
+async def _tool_list_materials(db: AsyncSession, tenant_id: str, query: str = "") -> str:
+    """List library materials with their aliases."""
+    sql = """
+        SELECT m.id, m.name, m.schaeffler_code, m.description,
+               COALESCE(
+                   (SELECT json_agg(ma.alias) FROM material_aliases ma WHERE ma.material_id = m.id),
+                   '[]'::json
+               ) AS aliases
+        FROM materials m
+        WHERE m.schaeffler_code IS NOT NULL
+    """
+    params: dict = {}
+    if query:
+        sql += """
+            AND (m.name ILIKE :q OR m.description ILIKE :q
+                 OR EXISTS (SELECT 1 FROM material_aliases ma WHERE ma.material_id = m.id AND ma.alias ILIKE :q))
+        """
+        params["q"] = f"%{query}%"
+    sql += " ORDER BY m.name LIMIT 30"
+
+    result = await db.execute(text(sql), params)
+    rows = result.mappings().all()
+    if not rows:
+        return json.dumps({"message": f"No materials found matching '{query}'.", "materials": []})
+
+    materials = []
+    for r in rows:
+        aliases = r["aliases"] if isinstance(r["aliases"], list) else []
+        materials.append({
+            "name": r["name"],
+            "schaeffler_code": r["schaeffler_code"],
+            "description": r["description"],
+            "aliases": aliases[:10],  # cap to avoid token bloat
+        })
+
+    return json.dumps({
+        "message": f"Found {len(materials)} material(s). Use the 'name' field for material_override.",
+        "materials": materials,
+    }, indent=2, default=str)
+
+
 async def _tool_find_product_renders(
     db: AsyncSession, tenant_id: str,
     product_name: str = "", product_id: str = "", transparent_only: bool = False,