docs(site): edit rules for clarity + cross-links; migrate off rules.txt

Editorial pass over site/ru/rules.md (on top of the verbatim port):
- moved the lore intro to the RU home page, rewritten in a modern voice;
- fixed typos, replaced the TODO/WTF cargo-tech note and the abandoned
  (---ссылка---) marker with the verified mechanic and a real cross-link,
  dropped the report TODO row;
- wove organic intra-page cross-links (#combat, #movement, #victory, ...);
- documented engine nuances verified against the code: ore auto-farming
  and the capital / "запасы промышленности" store (industry capped at
  population); cargo lost with ships destroyed in battle; and that a
  losing race's colonists at a neutral planet are NOT lost — they stay
  aboard (this corrects the audit note, verified in route.go).

Migration: delete game/rules.txt (its content now lives, authoritative,
in site/ru/rules.md) and repoint every reference to it (ui/frontend code
comments + tests, ui/docs, tools, ui/PLAN.md links). Record the
RU-authoritative rule in site/README.md and CLAUDE.md. The English
site/rules.md mirror follows in a separate stage.

ui/frontend/src/lib/active-view/table-races.svelte

@@ -8,7 +8,7 @@ immediately and the auto-sync pipeline drives the server in the
 background.
 
 The alliance graph and the 2/3 victory check are NOT computed
-here: `rules.txt` keeps each race's outgoing vote target private
+here: `site/ru/rules.md` keeps each race's outgoing vote target private
 (only the votes a race RECEIVED in the last tally and the local
 player's own pick are observable), and the acceptance criterion
 "vote counts match server state byte-for-byte" rules out