feat(modules): merge module OpenAPI fragments into /api/docs.json (phase 3, slice 5)

Core's half of the slice that closes phase 3. Two things: the request-time
fragment merge core has owed since phase 1, and the last of core's UO copy.

**The merge (MODULE_API.md §6.1a).** `swagger-output.json` is core's own routes
and cannot be anything else — it is generated on a developer's machine and
committed, so it must come out the same regardless of what they had checked out,
and a module arrives on a volume long after the image was built. Module routes
therefore reach the document at request time, from the `swagger-fragment.json`
each module ships: `swagger/docsSpec.js` merges the fragments of STARTED modules
over the committed spec, cached on a new loader state version and rebuilt when a
module's state moves.

Until now neither half existed. `swagger/mergeSpec.js` named the request-time
caller in its header and that caller was never written, so the 72 routes
module-uo serves were in no OpenAPI spec at all — core's standing rule ("never
ship a route that isn't in the spec") broken by the extraction rather than by a
route.

Core wins every key collision, `swagger-output.json` is never mutated (it is a
require()d JSON module — one in-place merge would be permanent AND cumulative),
and a fragment that is missing or unreadable costs that module its paths and
nothing else. The Swagger UI is now built per request for the same reason the
JSON is: bound once at require time it would show core's routes for the life of
the process while /api/docs.json showed the merged set.

**The last of core's UO copy** (slice 4 deferred it; §5.2's check reads code, not
prose, so none of this was caught):

- 31 UO schemas and 4 UO tags in `swagger/swagger.js`, describing routes core has
  not served since slice 1 — 578 lines. They moved to module-uo, namespaced
  `Uo…`, and arrive back through the merge on an instance that installs it.
- `info.description` said "a private Ultima Online shard".
- README.md's 48 UO mentions, including the architecture diagram and the whole
  `## Shard integration (uo-link)` section, now `## Modules`.
- `TOWNCRIER_DURATION_SEC` and `UOLINK_*` in the two `.env.example`s: read by the
  module, not by core, and documented in the module's README instead.

**Two dropped annotations, and the reason nobody knew.** swagger-autogen reports
an annotation it cannot parse and then prints Success in green, having skipped
it. `npm run swagger` now captures its diagnostics and fails — which immediately
found `POST /api/v1/admin/invites` and `POST /api/v1/auth/invite/:token/accept`
documented with an EMPTY request body, both since the day they were written.

Fixing the tag list also cleared five tags used by routes but never declared
(`Admin · Email`, `Admin · Invites`, `Admin · Moderation`, `Admin · Pages`,
`Auth · Me`) — the same defect class, in the other direction.

- 646 server tests (+9), 157 client tests unchanged
- routes.manifest.json unchanged (158 public + 2 internal); check:modules clean
- swagger-output.json: 128 paths, 69 schemas, 0 orphan tags, 0 orphan schemas
- verified against a real boot with module-uo installed: 197 merged paths
  (128 core + 69 module), all four module tags, 31 Uo schemas, no dangling $refs,
  /api/docs renders the module's operations with zero console errors

Refs: docs/website/MODULE_API.md §2.8, §6.1a; MODULE_SYSTEM.md §2.7.1

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

.env.example

@@ -33,8 +33,8 @@ LOG_FILE=app.log
 # BRAND_NAME / BRAND_CONTACT_EMAIL.
 BRAND_NAME=Runic Gateway
 BRAND_SHORT_NAME=Runic Gateway
-BRAND_TAGLINE=an independent private Ultima Online shard
-BRAND_DESCRIPTION=Runic Gateway — an independent private Ultima Online shard. News, screenshots, guides, and community notes.
+BRAND_TAGLINE=an independent game community
+BRAND_DESCRIPTION=Runic Gateway — an independent game community. News, screenshots, guides, and community notes.
 BRAND_CONTACT_EMAIL=
 BRAND_URL=
 # Accent color — drives the web theme's --accent and the Discord embed color.
@@ -107,20 +107,18 @@ CLIENT_ORIGIN=http://localhost:5173
 BOT_INTERNAL_URL=http://bot:4100
 BOT_INTERNAL_KEY=change-me-to-a-long-random-string
 
-# uo-link sidecar — the HTTP + WebSocket bridge to the ServUO game server. The
-# website ingests its live event feed and proxies its read queries/commands
-# (shard status, online players, player-vendor sales, IDOC houses, character
-# sheets, account linking, town-crier). In production the sidecar + shard run on
-# a DIFFERENT host from the website, so both URLs are configurable. The
-# shared-secret auth token is NOT an env var — it is entered in the admin panel
-# (Shard page) and stored encrypted in the DB (same pattern as the Discord bot
-# token). These URLs are just defaults; the admin can override them at runtime.
-UOLINK_BASE_URL=http://127.0.0.1:8080
-UOLINK_WS_URL=ws://127.0.0.1:8080/ws
-# Wire protocol this build speaks (3 = Protocol 3.0). Only a fallback for a site
-# with nothing saved yet — the admin panel's pinned value wins — but set it lower
-# if you deliberately run an older sidecar.
-UOLINK_PROTOCOL=3
+# ─── Installed modules ───
+# A module is a directory on the modules volume (see MODULES_DIR in
+# server/.env.example); everything about a specific game lives in one, and core
+# knows nothing about any of them. A module may read its own env vars, and they
+# belong here because Compose passes this file to the container.
+#
+# RunicGateway/Module-uo, for example, reads UOLINK_BASE_URL / UOLINK_WS_URL /
+# UOLINK_PROTOCOL as the defaults for its connection to a uo-link sidecar, and
+# TOWNCRIER_DURATION_SEC for its news leg. Its README documents them; they are
+# left out here rather than half-copied, because a copy of another repo's
+# settings is a copy that goes stale silently. With no module installed, none of
+# this applies and the site runs as core.
 
 # ─── Push notifications (M7) — self-hosted ntfy UnifiedPush relay ───
 # The `ntfy` compose service and the backend's push fan-out (opt-in notifications