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>

backend/app/converter/unity_scripts.py

@@ -98,8 +98,8 @@ class ScriptCodec:
             helper.read_typetree_boost, helper.get_ref_type_node = old_boost, old_resolve
 
     def read(self, obj):
-        from UnityPy.streams import EndianBinaryWriter
         from UnityPy.helpers import TypeTreeHelper as helper
+        from UnityPy.streams import EndianBinaryWriter
         # Bundles can retain exact schemas which differ from generated metadata
         # (notably editor-compiled Init). Prefer those schemas when available.
         self.templates = {(ref.m_AssemblyName.removesuffix(".dll"), ref.m_NameSpace, ref.m_ClassName): ref.node