feat: add Settings and Suite pages with comprehensive settings management and question suite builder

- Implemented SettingsPage for configuring default provider, temperature, and model paths.
- Added SuitePage for managing a suite of questions with features to add, edit, duplicate, and delete questions.
- Introduced TypeScript configuration files for app and node environments.
- Set up Vite configuration for development server with API proxying to backend.

server/main.py

@@ -0,0 +1,118 @@
+"""FastAPI application factory.
+
+In production the same process serves the JSON API and the compiled React
+bundle from ``web/dist``. During frontend development Vite serves the UI on its
+own port and proxies ``/api`` back here, so CORS is opened for localhost only.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import sys
+
+from fastapi import APIRouter, FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import FileResponse, JSONResponse
+from fastapi.staticfiles import StaticFiles
+from starlette.requests import Request
+
+from . import __version__
+from .api import router
+from .core_bridge import ROOT_DIR, ensure_directories
+from .plugins import get_plugin_manager
+
+WEB_DIST = ROOT_DIR / "web" / "dist"
+
+DEV_ORIGINS = [
+    "http://localhost:5173",
+    "http://127.0.0.1:5173",
+]
+
+
+def create_app() -> FastAPI:
+    ensure_directories()
+
+    app = FastAPI(
+        title="LM-Gambit",
+        description="Automated LLM diagnostic suite.",
+        version=__version__,
+        docs_url="/api/docs",
+        openapi_url="/api/openapi.json",
+    )
+
+    app.add_middleware(
+        CORSMiddleware,
+        allow_origins=DEV_ORIGINS,
+        allow_credentials=False,
+        allow_methods=["*"],
+        allow_headers=["*"],
+    )
+
+    app.include_router(router)
+    _mount_plugin_routes(app)
+
+    @app.get("/api/health")
+    async def health() -> dict:
+        return {"status": "ok", "version": __version__, "ui_built": WEB_DIST.is_dir()}
+
+    _mount_frontend(app)
+    return app
+
+
+def _mount_plugin_routes(app: FastAPI) -> None:
+    """Give each plugin defining register_routes its own /api/plugins/<slug>.
+
+    Routes are bound at startup, so a plugin that adds or changes endpoints
+    needs a server restart — unlike its other hooks, which reload live.
+    """
+    manager = get_plugin_manager()
+    for plugin in manager.with_hook("register_routes"):
+        plugin_router = APIRouter(
+            prefix=f"/api/plugins/{plugin.slug}",
+            tags=[f"plugin:{plugin.slug}"],
+        )
+        try:
+            plugin.module.register_routes(plugin_router)  # type: ignore[union-attr]
+        except Exception as exc:  # noqa: BLE001 - never let a plugin block startup
+            print(
+                f"[plugin:{plugin.slug}] register_routes() failed: {exc}",
+                file=sys.stderr,
+            )
+            continue
+        if plugin_router.routes:
+            app.include_router(plugin_router)
+
+
+def _mount_frontend(app: FastAPI) -> None:
+    assets_dir = WEB_DIST / "assets"
+    if assets_dir.is_dir():
+        app.mount("/assets", StaticFiles(directory=assets_dir), name="assets")
+
+    @app.get("/{full_path:path}", include_in_schema=False)
+    async def spa(request: Request, full_path: str) -> object:
+        if full_path.startswith("api/"):
+            return JSONResponse({"detail": "Not found."}, status_code=404)
+
+        index_file = WEB_DIST / "index.html"
+        if not index_file.is_file():
+            return JSONResponse(
+                {
+                    "detail": "Frontend not built.",
+                    "fix": "Run 'npm install && npm run build' inside web/, "
+                    "or start the Vite dev server with 'npm run dev'.",
+                },
+                status_code=503,
+            )
+
+        # Serve real files (favicon, manifest, …) directly; everything else
+        # falls through to index.html so client-side routing works on reload.
+        if full_path:
+            candidate = (WEB_DIST / full_path).resolve()
+            if candidate.is_file() and WEB_DIST.resolve() in candidate.parents:
+                return FileResponse(candidate)
+
+        return FileResponse(index_file)
+
+
+app = create_app()