Move dedupe cases fixture into web so docker build can see it

The PWA's names.test.ts imported internal/ai/harness/testdata/dedupe_cases.json,
which is outside the web build context the Dockerfile's web stage copies, so
tsc failed and docker build . failed. The single case file now lives at
web/src/dinners/testdata/dedupe_cases.json; the harness Go test reads it from
there, as TestLetterFoldsMatchPWA already reads letterFolds.json.

Maestro task: 3eee9f68-2d34-4e49-8ca5-43bacfb642f0

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -517,7 +517,7 @@ Regular has a name `harness.Similar` to it — the PWA's copy of the name
 rules in `web/src/dinners/names.ts` folds letters with
 `web/src/dinners/letterFolds.json`, which `gen_folds.py` writes from the
 same table as the server's, and runs the same cases,
-`internal/ai/harness/testdata/dedupe_cases.json`, as the server's) and
+`web/src/dinners/testdata/dedupe_cases.json`, as the server's) and
 notifications (`/onboarding/notifications`: what MealQuest notifies about,
 the iOS install hint, "Turn on notifications" and "Maybe later"). Either
 button sends `PATCH /api/v1/settings/household` with