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>

server/src/router/v1/admin/invites.router.js

@@ -19,7 +19,7 @@ invitesRouter.post(
   // #swagger.tags = ['Admin · Invites']
   // #swagger.summary = 'Create and email an account invite at a chosen access level'
   // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
-  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["email","role"], properties: { email: { type: "string" }, role: { type: "string" } } } } } */
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["email","role"], properties: { email: { type: "string" }, role: { type: "string" } } } } } } */
   /* #swagger.responses[201] = { description: 'Invite created', content: { "application/json": { schema: { type: "object", additionalProperties: true } } } } */
   /* #swagger.responses[400] = { description: 'Validation error', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
   adminOnly,

server/src/router/v1/auth/invite.router.js

@@ -33,7 +33,7 @@ inviteRouter.post(
   // #swagger.tags = ['Auth']
   // #swagger.summary = 'Accept an email invite (creates the account at the invited role)'
   // #swagger.description = 'Creates the website user at the invite’s pre-assigned role and logs them in (sets the session cookie). Bypasses the player_registration gate — the invite is its own authority. Rate limited + honeypot-guarded like registration.'
-  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["username","password"], properties: { username: { type: "string" }, password: { type: "string" } } } } } */
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["username","password"], properties: { username: { type: "string" }, password: { type: "string" } } } } } } */
   /* #swagger.responses[200] = { description: 'Account created and session issued', content: { "application/json": { schema: { $ref: "#/components/schemas/LoginResponse" } } } } */
   /* #swagger.responses[400] = { description: 'Validation error', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
   /* #swagger.responses[404] = { description: 'Invalid or expired invite', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */