remove origin validation

ALLOW_ANY_ORIGIN, ALLOW_ANY_ORIGIN_MUSIC, and everything they gated. The flag
defaulted to ON, so none of it ran on a real install — what comes out is
documented defence in depth that was already switched off. The file said so
itself: "Both flags and their call sites come out once the tailnet is the
perimeter."

Origin was never authentication here in any case. An app's `officer://<hex>`
origin is chosen by the client, forgeable outside a browser, and extractable from
a shipped binary.

Gone: the two flags, isOriginAllowed, isOriginCheckDisabled, isMusicOriginExempt,
originValidationMiddleware, ORIGIN_RULES and the whole OFFICER_<APP>_ORIGIN
scheme, PUBLIC_URL's origin/host derivation, and origin-validation.test.ts, which
existed only to pin them. CORS now echoes whatever Origin it is given, which is
what every install already did.

What SURVIVES is the reason this needed care. origin-validation.ts held two
unrelated things, and the second was the global authorization gate — a valid
non-owner token reaches only what its role grants, deliberately NOT under the
flag because it is account-based rather than origin-based. Its own comment called
it "the airtight half". Deleting the file wholesale would have deleted
authorization.

So it moves to _middlewares/capability-gate.ts as capabilityGateMiddleware, with
the name matching what it does: nothing in it reads an Origin header any more.
hono.ts mounts it in the same position, ahead of every router.

origin-middleware.ts stays and is untouched — it extracts the Origin for six auth
handlers that log it, and for passkeys. Extraction, not validation.

Also updates every claim that rested on the old model: CLAUDE.md's security
section and repo map, docs/secret-store.md, docs/mobile-api-keys.md, and five
messages in machine-setup's Tailscale section which told the owner to set
ALLOW_ANY_ORIGIN=false when declining a tailnet. That advice is now impossible to
follow, and the honest version is different: with no tailnet the token is the
whole lock, so put a proxy in front and restrict who can reach it.

Not typechecked (empty node_modules, frozen installs). Every changed file parses;
the setup section was run and writes four variables now.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup/machine-setup/machine-setup.sh

@@ -491,8 +491,8 @@ if ! skip; then
       if [[ "$TS_PLANE" == "none" ]]; then
         warn "no private network — Tailscale is installed but not connected"
         echo "     Connect it later with:  sudo tailscale up"
-        echo "     Remember ALLOW_ANY_ORIGIN=false and an HTTPS proxy in front of Officer."
-        SUMMARY+=("Tailscale: NOT connected by choice — no private network, ALLOW_ANY_ORIGIN must be set false")
+        echo "     Remember an HTTPS proxy in front of Officer, and restrict who can reach it."
+        SUMMARY+=("Tailscale: NOT connected by choice — no private network, so the token is the only lock")
         TS_CONNECT=false
       fi