docs: hygiene sweep - the four places the docs describe a site that no longer exists

Four documents still describe the pre-module-system website. None of them
misconfigures anything, which is why they survived; all four mislead a
reader trying to understand how the system is actually put together.

ARCHITECTURE.md placed shardIngest.js and uoLinkClient.js inside the
website backend. Both live in module-uo/server/utils/ - verified, they
are not in website/server/src at all. The document claimed to be "the
canonical copy of the diagram; the same diagram is embedded in the
website's README", and the two had silently diverged: the live README's
diagram has the module subgraph, the loader, and the game behind the
module, and this one did not. The diagram is now the live one verbatim,
the surrounding prose attributes the shard integration to the module, and
the intro no longer frames core as game-aware. The SSE bullet gains the
distinction the live README makes: the module declares which kinds are
public, core enforces the split.

website-README.md had drifted from the live README by 28 lines, all of
them the "Three ways in, and none of them is a build" section - the admin
panel, the MODULES environment variable, and by hand - which is now the
primary module-install story. Re-synced verbatim, since a faithful
snapshot is the file's whole purpose. The diff was purely additive; the
snapshot contained nothing the live README had dropped.

README.md's index was missing thirteen documents, not the four the audit
had found: TEAMS.md, ARCHITECTURE.md, TRUSTED_DEVICES_MFA.md and
MODERATION_APPEALS.md, and also link/v4.md - the current protocol -
android/THEMING_AND_NAV.md, ci/SONARQUBE.md, installer/PROJECT_TREE.md,
modules/kit-acceptance.md, modules/uo/API.md, modules/uo/SCHEMA.md,
website/test-plan.md and the two API_V2 documents. The layout block
already advertised a ci/ directory that had no section. Every markdown
file outside the issue templates is now indexed, and every link resolves.
API_V2_SKELETON.md is listed as superseded, which is what its own header
says.

BACKEND_DESIGN.md was titled "UOMysticmoon Website - Backend Design"
though it is core's contract and core is game-agnostic. Retitled, with a
note that nothing in it is instance-specific. Its hardcoded public
contact address is now described as what it is - seeded from
BRAND_CONTACT_EMAIL into the contact_email setting, with UOMysticmoon as
the example instance.

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

website/BACKEND_DESIGN.md

@@ -1,9 +1,14 @@
-# UOMysticmoon Website — Backend Design
+# Runic Gateway Website — Backend Design
 
 > Phase 1 of 3: **backend design** → Claude Design (frontend mockup) → coding.
 > This document is the contract the later phases build against.
 
-Public contact email: **UOMysticmoon@gmail.com**
+**This is core's contract, and core is game-agnostic.** Nothing here is specific to any one game or
+instance: the site's name, colours, logo and public contact address are data
+(`BRAND_*` / the `settings` table), and everything about a *particular* game arrives from an
+installed module — see [MODULE_SYSTEM.md](MODULE_SYSTEM.md) and, for the worked example,
+[../modules/uo/](../modules/uo/README.md). **UOMysticmoon** is the first instance, and appears
+below only as an example value.
 
 ---
 
@@ -272,7 +277,8 @@ Seeded with the 8 spec categories: `new-player-guide, maps-atlas, systems, items
 
 Seeded keys: `site_mode` (default `maintenance`), `site_mode_changed_at`,
 `site_mode_changed_by`, `maintenance_message`, `status_message`, `homepage_teaser`,
-`contact_email` (=UOMysticmoon@gmail.com), `site_title`, `player_registration`
+`contact_email` (seeded from `BRAND_CONTACT_EMAIL`; e.g. `UOMysticmoon@gmail.com` on the first
+instance), `site_title`, `player_registration`
 (default `disabled`), `mobile_app_links_enabled`, `module_source_hosts`.
 
 `module_source_hosts` is the allowlist of hostnames a module may be installed from