chore: add CI, lint config, login rate limit and split large modules

- Rate-limit failed logins (8 per 15 min per IP or username, 429 + Retry-After)
- Add ruff/mypy config and GitHub Actions workflow (ruff, pytest, tsc, tests, build)
- Apply ruff autofixes (import order, pyupgrade)
- Extract rpy_helpers.py, engine-util.ts, TranslationParts.tsx and
  translation-types.ts from oversized modules
- Add dependency-free React UI tests
- Refresh README and ARCHITECTURE (Naninovel/Tomie, status and plans)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

frontend/tests/ui.test.mjs

@@ -0,0 +1,42 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { fileURLToPath } from "node:url";
+import { build } from "esbuild";
+
+// Bundle React together with the code under test so that both share one React instance.
+async function load(entry) {
+  const result = await build({
+    stdin: { contents: entry, resolveDir: fileURLToPath(new URL("../src/", import.meta.url)), loader: "tsx" },
+    bundle: true, write: false, format: "esm", platform: "node", jsx: "automatic", logLevel: "silent",
+    banner: { js: "import { createRequire } from \"node:module\"; const require = createRequire(process.cwd() + \"/package.json\");" },
+  });
+  const code = Buffer.from(result.outputFiles[0].text).toString("base64");
+  return import(`data:text/javascript;base64,${code}`);
+}
+
+const { renderToStaticMarkup, h, ProgressBar, highlight } = await load(`
+  export { renderToStaticMarkup } from "react-dom/server";
+  export { createElement as h } from "react";
+  export { ProgressBar, highlight } from "./pages/TranslationParts";
+`);
+
+const stats = {
+  lines: 10, translated: 5, progress: 0.5, strings: 4, stringsTranslated: 2,
+  states: { untranslated: 5, outdated: 1, translated: 3, fuzzy: 0, machine: 0, approved: 1 },
+};
+
+test("ProgressBar renders counts and only non-empty segments", () => {
+  const html = renderToStaticMarkup(h(ProgressBar, { stats }));
+  assert.match(html, /5 из 10 реплик \(50%\)/);
+  assert.match(html, /устарело 1/);
+  assert.match(html, /seg-approved/);
+  assert.doesNotMatch(html, /seg-warn/);
+});
+
+test("highlight wraps glossary terms case-insensitively and escapes regex characters", () => {
+  const terms = [{ src: "Eileen", t: "Эйлин", note: "" }, { src: "a+b", t: "x", note: "" }];
+  const html = renderToStaticMarkup(h("p", null, highlight("eileen met a+b", terms)));
+  assert.match(html, /<mark title="Эйлин">eileen<\/mark>/);
+  assert.match(html, /<mark title="x">a\+b<\/mark>/);
+  assert.equal(highlight("plain", []), "plain");
+});