Add rulebook RAG pipeline and LLM-driven game setup wizard

RAG: switch Postgres to pgvector, chunk and embed the three D&D
rulebooks locally via sentence-transformers, and retrieve relevant
excerpts per DM turn (query = latest player message) to ground the
system prompt. Retrieval runs off the event loop and is capped by a
relevance threshold and a max character budget so it can't blow up
context size or cost.

Game setup wizard: creating a game now opens a short chat where the
DM asks about genre, length, and the player's experience level, then
proposes a name and description via a tool call. The player can edit
both before creating the game. Stateless endpoint — the frontend
carries the conversation, no DB needed since the game doesn't exist
yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/GamesList.tsx

@@ -1,8 +1,9 @@
-import { FormEvent, useEffect, useState } from "react";
+import { useEffect, useState } from "react";
 import { useNavigate } from "react-router-dom";
 
-import { createGame, Game, listGames } from "../api/games";
+import { Game, listGames } from "../api/games";
 import GameCard from "../components/GameCard";
+import GameSetupChat from "../components/GameSetupChat";
 
 export default function GamesList() {
   const navigate = useNavigate();
@@ -10,10 +11,6 @@ export default function GamesList() {
   const [loading, setLoading] = useState(true);
   const [showCreate, setShowCreate] = useState(false);
 
-  const [name, setName] = useState("");
-  const [description, setDescription] = useState("");
-  const [error, setError] = useState<string | null>(null);
-
   async function load() {
     setLoading(true);
     try {
@@ -27,17 +24,6 @@ export default function GamesList() {
     load();
   }, []);
 
-  async function handleCreate(e: FormEvent) {
-    e.preventDefault();
-    setError(null);
-    try {
-      const game = await createGame(name, description);
-      navigate(`/games/${game.id}`);
-    } catch {
-      setError("Spiel konnte nicht erstellt werden.");
-    }
-  }
-
   return (
     <div className="mx-auto max-w-3xl px-4 py-8">
       <div className="mb-6 flex items-center justify-between">
@@ -52,32 +38,7 @@ export default function GamesList() {
         </div>
       </div>
 
-      {showCreate && (
-        <form onSubmit={handleCreate} className="mb-6 flex flex-col gap-3 rounded-lg border border-slate-800 bg-slate-900 p-4">
-          <input
-            required
-            placeholder="Name des Spiels"
-            value={name}
-            onChange={(e) => setName(e.target.value)}
-            className="rounded bg-slate-800 px-3 py-2 outline-none focus:ring-2 focus:ring-amber-400"
-          />
-          <textarea
-            placeholder="Kurzbeschreibung (Genre, Welt, ...)"
-            value={description}
-            onChange={(e) => setDescription(e.target.value)}
-            className="rounded bg-slate-800 px-3 py-2 outline-none focus:ring-2 focus:ring-amber-400"
-            rows={3}
-          />
-          <button
-            type="submit"
-            className="self-start rounded bg-amber-500 px-3 py-2 text-sm font-semibold text-slate-950 hover:bg-amber-400"
-          >
-            Erstellen
-          </button>
-        </form>
-      )}
-
-      {error && <p className="mb-4 text-sm text-red-400">{error}</p>}
+      {showCreate && <GameSetupChat onCreated={(game) => navigate(`/games/${game.id}`)} />}
 
       {loading ? (
         <p className="text-slate-400">Lädt…</p>