Count the visits, and say whether anyone got anywhere

A hosted demo raises a question a local app never does: is anyone using it,
and do they reach the part that matters? `/analytics` answers it — visitors,
pages, referrers, countries, devices, which shared scenarios get played, turns
and demo-key spend, API and turn errors, and a funnel from visited to played a
turn to signed up.

Not a third-party script, for reasons specific to this one. The CSP allows
`script-src 'self'`, so a tracker means loosening it; adblockers eat the
popular ones, which silently biases exactly the technical audience this
project gets shown to; and none of them can see the measurement that actually
matters here, which is a turn, not a pageview.

**A visit is a write and never a read.** After the 189x egress fix it would be
perverse to add a feature that reads rows per request, so counts accumulate in
a process-local dict and flush every 60s as UPSERTs. Storage is a generic
`(day, metric, label) -> hits` counter, so measuring something new later costs
a constant rather than a migration, plus one row per visitor per day for the
funnel flags. Every dashboard query is a GROUP BY returning tens of rows
however much traffic sits behind it; a month reads back in a few kilobytes.
The buffer's cost is that a hard restart can lose up to a minute — the flusher
also runs on shutdown, and a tier that sleeps when idle sleeps on an empty
buffer anyway.

**The counters are anonymous; the access log beside them is not, on purpose.**
A visitor is `HMAC(secret, "visitor:<user id>")` truncated to 32 chars —
one-way, so `analytics_daily` and `analytics_visitor_days` cannot be joined
back to `users`, and keyed, so no client can compute one. Story content never
reaches that module, and the only content it ever names is a seeded public
scenario's title; a player's own titles are theirs. `accesslog.py` is the
identifying half and is a separate module writing a separate table so that
separation is a property of the code rather than a convention: `access_events`
records sessions, sign-ins, registrations and failed attempts with address,
email and device, read on a second tab of the same page behind the same gate.

Both halves are gated on `AIDND_ANALYTICS_EMAILS`, not `POWER_USERS`. An
unmetered tester is not automatically someone who should see the traffic. The
route 404s and the nav link is absent for everyone else, the same treatment
AI Chat gets; unset in a hosted deploy means nobody sees it, including me.

Three things came out of building it that a test would not have suggested.

**A failed turn is an HTTP 200 with a bad ending.** The status-code middleware
cannot see one, so a demo whose model had started refusing every request would
look perfectly healthy from outside. All five SSE error paths in
`_generate_turn` now go through a `turn_error()` helper that counts on the way
out. Error buckets elsewhere are labelled by the matched route template rather
than the requested path — one bucket per endpoint instead of one per adventure
id, and, the reason it isn't merely tidier, an unmatched path is entirely
attacker-chosen, so labelling by it would let anyone mint rows.

**The funnel counts people, not clicks.** A player who starts six adventures
is one person who started an adventure. That is the whole reason the
per-visitor-day table exists; its flags only ever turn on, and `is_new` is
settled by the first write of a visitor's first day.

**The tests run on SQLite and production is Neon.** A flush that raises is
caught and logged, so a dialect mistake in the UPSERTs would have stayed
invisible until the dashboard quietly never filled.
`test_the_upserts_compile_for_postgres` compiles both statements against the
Postgres dialect without connecting to one.

Two things this leans on elsewhere. `limits._client_ip` is now public
`client_ip`: the access log needs the same answer, and two functions both
deciding which hop is the caller's is how one of them ends up trusting a
header it shouldn't. And the cleanup sweeper now starts if *either* job has
work — a deployment can keep every guest forever and still want its
visitor-day rows aged out.

No migration. Both tables are new and `bootstrap()` calls `create_all` on
existing databases too, the route `branches` took in Phase 14, so
`LATEST_VERSION` is still 64.

497 tests green, frontend lint and build clean, driven by hand against a
synthetic 90-day fixture at 1568px. The narrow-screen layout follows the
existing 720px block but is unverified: `resize_window` is ignored on a
maximized Chrome and `frame-ancestors 'none'` rules out checking it in a sized
iframe. Also repaired here: a rename in test_ratelimit_hardening.py had run
through the test names themselves, leaving `testclient_ip_*` — still collected
by pytest, which is why it passed unnoticed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DfMCsN1KBLsTqMkj5hSgrY

backend/tests/test_ratelimit_hardening.py

@@ -3,7 +3,7 @@ per-account login throttle added to close it.
 
 Background: uvicorn's --forwarded-allow-ips "*" trusted the LEFTMOST
 X-Forwarded-For entry, which the client controls, so rotating the header
-handed out a fresh rate-limit bucket per request. _client_ip now reads the
+handed out a fresh rate-limit bucket per request. client_ip now reads the
 hop the trusted edge appends (rightmost), and login has an email-keyed throttle
 that no IP trick can dilute.
 
@@ -31,22 +31,22 @@ class _Req:
         self.client = None if peer is None else type("C", (), {"host": peer})()
 
 
-# ---------- _client_ip: the spoof-resistant hop ----------
+# ---------- client_ip: the spoof-resistant hop ----------
 
 def test_client_ip_takes_appended_rightmost_hop(monkeypatch):
     monkeypatch.setattr(limits, "TRUSTED_PROXY_HOPS", 1)
     # Attacker prepends a fake IP; the edge appends the real one on the right.
     req = _Req("203.0.113.9, 198.51.100.77")
-    assert limits._client_ip(req) == "198.51.100.77"
+    assert limits.client_ip(req) == "198.51.100.77"
 
 
 def test_client_ip_ignores_spoofed_leftmost(monkeypatch):
     monkeypatch.setattr(limits, "TRUSTED_PROXY_HOPS", 1)
     # Whatever the client stuffs to the left, the keyed IP stays the real hop —
     # so rotating it no longer mints a new bucket.
-    a = limits._client_ip(_Req("1.1.1.1, 198.51.100.77"))
-    b = limits._client_ip(_Req("2.2.2.2, 198.51.100.77"))
-    c = limits._client_ip(_Req("evil, junk, 198.51.100.77"))
+    a = limits.client_ip(_Req("1.1.1.1, 198.51.100.77"))
+    b = limits.client_ip(_Req("2.2.2.2, 198.51.100.77"))
+    c = limits.client_ip(_Req("evil, junk, 198.51.100.77"))
     assert a == b == c == "198.51.100.77"
 
 
@@ -54,12 +54,12 @@ def test_client_ip_honours_extra_trusted_hops(monkeypatch):
     monkeypatch.setattr(limits, "TRUSTED_PROXY_HOPS", 2)
     # Two trusted hops: real client is second from the right.
     req = _Req("9.9.9.9, 203.0.113.5, 198.51.100.77")
-    assert limits._client_ip(req) == "203.0.113.5"
+    assert limits.client_ip(req) == "203.0.113.5"
 
 
 def test_client_ip_falls_back_to_socket_peer():
-    assert limits._client_ip(_Req(None, peer="172.16.0.4")) == "172.16.0.4"
-    assert limits._client_ip(_Req(None, peer=None)) == "unknown"
+    assert limits.client_ip(_Req(None, peer="172.16.0.4")) == "172.16.0.4"
+    assert limits.client_ip(_Req(None, peer=None)) == "unknown"
 
 
 # ---------- per-account login throttle ----------