Finish the contract ratchet, the upload bridge and the client leftovers

BODY_CONTRACT_ALLOW_LIST is empty. The last seventeen handlers type their
body with a createZodDto class, so the fail-closed boot gate has nothing left
to forgive; it still refuses a boot for a new handler that reads @Body()
without one.

Several of those contracts describe rather than constrain, and that is the
whole care in this change. The pipe runs before the handler, so a schema
stricter than the handler moves a user-visible answer:

- TagsController.create answers { error: 'Tag name is required' }, pinned
  byte-for-byte in two tests, and the pipe formats as `field: message`. The
  DTO leaves name optional and the handler keeps the check that owns the
  message. Same shape for the booking-import confirm body, which additionally
  gains per-item validation the handler never did.
- PluginsController.activate and install answer 503 when plugins are disabled,
  and check that BEFORE looking at the body. A schema that rejected first
  would turn that into a 400 for an operator whose server has plugins off.
- setEgressHosts reads a non-array `hosts` as "clear the list", which is the
  documented reset. Typing it as string[] would have removed a working admin
  action rather than tightened anything.
- PluginRoutesController.route answers { route: null } at 200 for everything
  it dislikes, so the client falls back to straight lines. A 400 there would
  turn a graceful degradation into a visible error.

files.bridge is gone. The multer options are built by
MulterModule.registerAsync from an AllowedFileTypesService leaf, so the
fileFilter reads the operator's extension list from the container instead of
from a second FilesService built outside it. Nest injects
MULTER_MODULE_OPTIONS with @Optional(), so a token that fails to resolve is
not a boot error: it silently falls back to defaults, with no filter and no
size cap. FILE-020 already proved that for trip files by uploading an .svg
over HTTP and expecting 400; journey uploads had no such case, and now do.
VIDEO_UPLOAD is untouched, including the filename callback that forces .jpg
regardless of what the client sends, which guards the public share proxy.

PluginFrame gets an onError. A frame whose document fails to load left a
blank element at full height, which reads as a hung app rather than as a
plugin that is gone.

typecheck:tests runs in CI now, with the test tree at zero errors. tz-lookup
is left as it is: the build puts it in a lazy helpers chunk, not the entry
chunk, and the remaining split would trade a synchronous render for an async
one to move 172 kB that is already off the critical path.

server/package.json

@@ -9,6 +9,7 @@
     "start:prod": "node --require tsconfig-paths/register dist/index.js",
     "reset-admin": "node reset-admin.js",
     "typecheck": "tsc --noEmit",
+    "typecheck:tests": "tsc -p tsconfig.tests.json --noEmit",
     "gen:plugin-facts": "node --import tsx scripts/gen-plugin-facts.ts",
     "check:plugin-facts": "node --import tsx scripts/gen-plugin-facts.ts --check",
     "format": "prettier --write \"src/**/*.ts\" \"test/**/*.ts\"",