M2: cut the hosted product away from the local one

94 files, +1,395 -6,578. Three files are new; twenty-four are gone. The
milestone is subtraction, and what is left is the single-user local
storyteller the specification describes.

Removed in full: campaign scripting and its QuickJS sandbox; multi-user
accounts, guest sessions, login, registration and the shared demo key;
the visitor-analytics tables, dashboard and page beacon; the access log
of sign-ins, addresses and devices; per-IP and per-user rate limiting
and quotas; Render deployment config; Postgres and psycopg; cloud
inference providers, the API-key field and the key encryption that
existed to store it; session-cookie signing. None of it was hidden
behind a flag — the routes are gone and answer 404.

Two things were kept that the brief allowed keeping. The `users` table
and its foreign keys stay as an internal ownership detail, because
rewriting them out means a migration across most of the schema to
delete a column that costs nothing; nothing creates a second user and
no request carries an identity. Five inert tables and four inert
columns stay for the same reason, so an M1 campaign database opens
unchanged.

The one addition is app/endpoints.py, which decides where a story may
be sent. Loopback, RFC1918, link-local, unique-local and CGNAT — an
explicit allowlist of networks, not a guess at what `ipaddress` means
by "private", which calls the documentation ranges private and IPv6
loopback reserved. Every address a hostname resolves to must be in it,
so a split answer does not squeak through, and the rule runs both when
the endpoint is saved and before every outbound request, because a name
that resolved to the LAN this morning can resolve elsewhere this
afternoon. Known cloud hosts are named in the refusal so the error says
why rather than looking like broken DNS. TLS is never traded against
it: M1's shared trust context is intact on all four clients and there
is no way to skip verification.

The hardcoded 120-second model timeout is now a setting. That was not
theoretical — on this GPU-less four-core host a cold load of
qwen2.5:3b-instruct took 648.9 seconds to produce the first turn, while
turns 2 to 5 of the same campaign took 3.6 to 13.1. Connect stays short
at 10s so a wrong address still fails fast; the read timeout defaults
to 300s and is bounded at 3600, because "wait longer" must stay a
number.

Two defects found while testing and fixed here. An unknown /api path
fell through the SPA catch-all and came back as HTML with status 200,
so a client asking for JSON parsed a web page instead of learning the
route was gone. And AIDND_CORS_ORIGINS accepted "*", which on an
unauthenticated loopback API would hand every page on the Internet a
write handle on the campaign database; it now refuses to start.

Verified rather than assumed. Offline, on a network with no route out
and no DNS: five turns, retry with both takes retained, restart with an
identical transcript digest, a failed model call leaving the accepted
AI-turn count untouched, and a capture with zero non-loopback unicast
packets. Against a real second machine on the LAN over HTTPS with a
private CA: four turns, restart, and a capture showing 289 packets to
the approved host, 344 loopback, zero anywhere else, zero DNS queries.
Cloud and public endpoints refused with their reasons; no API key
settable; every removed route 404.

604 backend tests pass, down from 648 by the fifteen retired with the
subsystems they tested and up by the twenty-nine added for the endpoint
policy and the removed surface. The scripting tests were not deleted:
eight files used a JavaScript counter as instrumentation for the state
snapshot and rollback machinery, which M2 does not touch, so the
counter moved to the world-state engine and those tests still assert
what they always did. Frontend lint and build are clean; the image
builds, and its wheel-building stage is gone with quickjs.

No M3 work. Undo is still destructive and there is still no Redo.

DEVELOPMENT.md

@@ -46,6 +46,9 @@ ollama pull qwen2.5:3b-instruct
 ollama pull nomic-embed-text      # only if you want the memory bank
 ```
 
+There is no account to create and nothing to log in to. The application is
+single-user: whoever can reach it on loopback is its owner.
+
 ## Running
 
 **Development** — backend on `:8000`, Vite dev server on `:5173`:
@@ -102,7 +105,37 @@ curl -X PUT http://127.0.0.1:8000/api/settings \
 
 `POST /api/settings/test` (the **Test connection** button) returns
 `{"ok": true, "models": [...]}` and is the fastest way to tell a wrong endpoint
-from a missing model.
+from a missing model. When it fails it says which kind of failure it was, and
+they need different things done about them:
+
+| `kind` | What it means |
+| --- | --- |
+| `rejected` | The endpoint is outside the policy below. Not a network problem. |
+| `unreachable` | Nothing answered. Ollama is not running there, or the port is wrong. |
+| `tls` | The certificate did not verify — install the CA (see below). |
+| `timeout` | It accepted the connection and then said nothing. |
+| `http` | It answered with an error status; the body is included. |
+
+A successful test also warns when the endpoint is reachable but has no model by
+the configured name, which is the commonest way for a correct endpoint to still
+fail every turn.
+
+### Which endpoints are allowed
+
+`backend/app/endpoints.py` decides, and it is deliberately narrow: **loopback,
+your own LAN, or nothing.** The allowed networks are `127.0.0.0/8`, the three
+RFC1918 ranges, link-local, IPv6 loopback and unique-local, and `100.64.0.0/10`
+(carrier-grade NAT, which is what a mesh VPN such as Tailscale hands out).
+
+Every address the endpoint's hostname resolves to must be in one of them. A
+public address is refused, a name resolving to both a private and a public
+address is refused, and known cloud inference hosts are refused by name so the
+error says why rather than looking like a DNS fault.
+
+The rule is applied when you save the endpoint *and* again before every
+outbound request, so a database edited by hand or a hostname that starts
+resolving somewhere new cannot turn a local install into an exfiltration path.
+There is no setting to relax it.
 
 ### Same host (the default)
 
@@ -137,9 +170,8 @@ Use an IP address or a name your own network resolves. Then:
 - the inference machine needs the models installed, not the storyteller;
 - no Internet is involved in either direction.
 
-`app/netguard.py` refuses private addresses only in hosted multi-user mode
-(`AIDND_MULTI_USER=1`), which local installs never turn on, so a LAN endpoint
-is accepted as configured.
+A LAN endpoint is accepted because it is on one of the allowed networks above.
+Nothing else about it is special.
 
 #### If that endpoint is HTTPS with your own CA
 
@@ -176,7 +208,7 @@ visible from within.
 ## Tests
 
 ```bash
-cd backend && .venv/bin/python -m pytest tests/ -q     # 648 tests
+cd backend && .venv/bin/python -m pytest tests/ -q     # 604 tests
 cd frontend && npm run lint && npm run build
 ```
 
@@ -192,6 +224,14 @@ suite as complete evidence.
 is lost from the union, or if a new HTTP client is added without the shared
 verification context.
 
+M2 added two more. `test_endpoint_policy.py` fails if the set of reachable
+addresses widens, or if either place the rule is applied stops applying it —
+it resolves hostnames through a stub, so it tests the policy rather than
+whatever DNS the machine has. `test_local_only_surface.py` fails if a removed
+subsystem comes back as a route, if an API key becomes settable again, if the
+model timeout stops being configurable or becomes unbounded, or if a supported
+start path stops binding loopback.
+
 ## What was made offline-safe, and how to check
 
 Two runtime downloads were removed in Milestone M1. Both were invisible on a