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/internal/storage/sqlstore/sqlstore.go

@@ -35,6 +35,16 @@ type Options struct {
 	// Settings holds the statements for the server_settings table.
 	Settings SettingsQueries
 
+	// Rebind translates the `?` placeholders that the shared component
+	// stores are written with into this driver's style. SQLite needs no
+	// translation and leaves it nil; PostgreSQL turns them into $1, $2...
+	Rebind func(query string) string
+
+	// IsUniqueViolation recognises this driver's unique-constraint error, so
+	// that a taken user name can be told apart from a database failure
+	// without a check-then-insert race.
+	IsUniqueViolation func(error) bool
+
 	// Logger is used for migration progress.
 	Logger *slog.Logger
 }
@@ -46,6 +56,7 @@ type Store struct {
 	db       *sql.DB
 	log      *slog.Logger
 	settings *Settings
+	users    *Users
 }
 
 // New builds a Store. It does not touch the database.
@@ -61,6 +72,7 @@ func New(opts Options) (*Store, error) {
 		db:       opts.DB,
 		log:      opts.Logger,
 		settings: NewSettings(opts.DB, opts.Settings),
+		users:    NewUsers(opts.DB, opts.Rebind, opts.IsUniqueViolation),
 	}, nil
 }
 
@@ -79,6 +91,9 @@ func (s *Store) Close() error { return s.db.Close() }
 // Settings implements storage.Database.
 func (s *Store) Settings() storage.SettingsStore { return s.settings }
 
+// Users implements storage.Database.
+func (s *Store) Users() storage.UserStore { return s.users }
+
 // Migrate implements storage.Database.
 func (s *Store) Migrate(ctx context.Context) error {
 	ms, err := s.migrations()