Phase 1: accounts and sessions

Implements PLAN.md Phase 1. A client can now register, log in, manage its
devices and set its profile; an operator can create accounts and flip the
runtime switches. There are still no rooms and no real /sync.

userapi: accounts, argon2id passwords in PHC format, devices, access and
refresh tokens stored as SHA-256 hashes, account data and the admin flag.
Its storage interface is storage.UserStore, implemented once in sqlstore
with `?` placeholders; the postgres driver supplies a rebind function and
unique-violation recognition rather than keeping a second copy of thirty
statements. Timestamps in these tables are int64 milliseconds, the unit the
Client-Server API uses on the wire.

Client-Server API: register (user-interactive auth with m.login.dummy and
optional registration tokens), register/available, token validity, login
with m.login.password, logout, logout/all, refresh, account/whoami,
capabilities, devices/* with password-gated deletion, profile/*, global and
per-room account data.

GET /sync is a deliberate placeholder: it answers a valid token with an
empty but well-formed response and refuses a revoked one. Phase 1 has no
rooms, so that is the whole truth, and it is what makes session revocation
observable. Phase 4 replaces it with the syncapi.

Auth middleware resolves a bearer token (header or the legacy query
parameter) to a device and user, answering an expired token with the soft
logout the spec asks for. Rate limiting is a token bucket per endpoint class
keyed on the client address, returning M_LIMIT_EXCEEDED with retry_after_ms.

adminapi v1 under /_warp/admin/v1: admin-only auth via a normal Matrix
token, GET/PUT /federation and /registration driving internal/settings and
reporting a config-pinned switch as a 409, GET/POST /users, GET /stats.

warp create-account [--admin] creates the first account straight in the
database, so a new install with registration off has a way in.

Complement is wired up for the federation=off profile: an image meeting its
contract, an entrypoint that configures Warp entirely from WARP_*
variables, and a runner that builds, clones and executes the target set
(TestRegistration, TestLogin, TestDeviceManagement). It has not been run
yet -- there is no container runtime on the development machine -- so the
three tests' assertions were read from the Complement sources and pinned as
httptest tests instead, and CI gained a job that runs the real thing.

Also fixes a .gitignore bug from Phase 0: the unanchored `warp` pattern,
meant for the built binary, also matched the directory server/cmd/warp and
silently excluded the entire command package from the repository. The
binary patterns are now anchored to the repository root, and cmd/warp is
committed for the first time.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/test/complement/Dockerfile

@@ -0,0 +1,60 @@
+# Warp as a Complement homeserver image.
+#
+# Complement (https://github.com/matrix-org/complement) is the official
+# Matrix integration suite: it runs one container per homeserver per test and
+# drives it over the real HTTP API. Its image contract is short, and this
+# file exists to meet it:
+#
+#   - EXPOSE 8008 (client) and 8448 (federation).
+#   - Take the server name from the SERVER_NAME environment variable.
+#   - Keep storage inside the container.
+#   - Survive the entrypoint being run more than once.
+#   - Answer GET /_matrix/client/versions with a 200.
+#
+# Build it from the repository root, because the build context is the Go
+# module one directory up:
+#
+#   docker build -t complement-warp -f server/test/complement/Dockerfile .
+#
+# Federation (port 8448, served over TLS with a certificate signed by the CA
+# Complement mounts at /complement/ca) arrives in Phase 5. Until then this
+# image is for the federation=off profile: the C-S tests. The port is still
+# exposed, because Complement expects it to be.
+
+FROM golang:1.26-alpine AS build
+
+# The workspace file is not copied, so the build must not look for one.
+ENV GOWORK=off
+ENV CGO_ENABLED=0
+
+WORKDIR /src
+
+# Dependencies first, so that editing Go sources does not re-download them.
+COPY server/go.mod server/go.sum ./
+RUN go mod download
+
+COPY server/ ./
+RUN go build -trimpath -o /out/warp ./cmd/warp
+
+FROM alpine:3.21
+
+# curl is what the health check uses; ca-certificates is for the outbound
+# federation requests of Phase 5.
+RUN apk add --no-cache ca-certificates curl
+
+COPY --from=build /out/warp /usr/local/bin/warp
+COPY server/test/complement/entrypoint.sh /usr/local/bin/warp-complement
+RUN chmod +x /usr/local/bin/warp-complement
+
+# Everything mutable lives here: the SQLite database and the signing key.
+VOLUME /data
+
+EXPOSE 8008 8448
+
+# Complement waits for the container to become healthy before it starts a
+# test, so the interval is short and the retries generous: a cold start has
+# to run the migrations first.
+HEALTHCHECK --interval=1s --timeout=2s --start-period=1s --retries=60 \
+	CMD curl -fsS http://localhost:8008/healthz || exit 1
+
+ENTRYPOINT ["/usr/local/bin/warp-complement"]