feat: interactive JSON / JSON5 mode selector at build time

Lets the operator pick between strict JSON (legacy) and JSON5 for every
configuration file consumed by Nitro and the renderer.

- scripts/configure-json.mjs: interactive prompt (JSON5 recommended),
  with --if-missing and --non-interactive flags for CI use
- package.json: yarn configure / prestart / prebuild hooks
- vite.config.mjs: reads .nitro-build.json (or NITRO_JSON_MODE env) and
  injects the compile-time constant __NITRO_JSON_MODE__ via define
- src/bootstrap.ts: routes client-mode.json parsing through the
  selected mode
- .gitignore: ignore the per-deployment .nitro-build.json
- README: full usage and override section
- public/configuration assets regenerated by the updated prebuild flow

The renderer side (@nitrots/utils JsonParser) is updated in the
companion Nitro_Render_V3 commit on the dev branch.

public/configuration/bootstrap.js

@@ -1,17 +1,4 @@
 (() => {
-  const API_BASE = "http://localhost:2096";
-
-  const ensureMobileViewport = () => {
-    let viewport = document.querySelector('meta[name="viewport"]');
-    if(!viewport) {
-      viewport = document.createElement("meta");
-      viewport.name = "viewport";
-      document.head.appendChild(viewport);
-    }
-    viewport.content = "width=device-width, initial-scale=1, viewport-fit=cover";
-  };
-
-  ensureMobileViewport();
   const FALLBACK_API_BASE = "";
 
   const getBase = () => {