feat(auth): add velodrome create-admin to bootstrap the first user

A fresh deployment could not be used. Registration requires a valid invite
code, invites can only be issued by an existing admin, and a newly migrated
database has neither -- so there was no way to create the first account.
docs/PLAN.md always called for this command; it was never built during
Phase 0, and D16 (single-container deploy) made the gap reachable.

Adds a console script -- `[project.scripts]` -> velodrome.cli:main -- which
installs into the same venv as alembic and uvicorn, so the deployed image
already has it on PATH:

    docker exec -it velodrome velodrome create-admin --email you@example.com

The account-creating logic is `auth.service.create_admin`, not something in
cli.py, so that `db.auth_session` stays confined to auth/service.py as its
docstring requires. Its lookup is an exact match on a unique key, which is
the pattern db.py documents as safe on that session.

Deliberate constraints, all covered by tests (see docs/DECISIONS.md D18):

- Refuses an email that already exists rather than updating the row. An
  operator re-running a months-old command from shell history means "create",
  never "reset the password"; silently accepting would make this an
  undocumented password-reset tool that any container-exec grants.
- Not restricted to "only when there are zero users". The restriction buys
  nothing -- reaching the command already requires process execution inside
  the container, which already permits rewriting the SQLite file directly --
  while removing the cases that do happen: a second admin, and recovering an
  instance whose only admin was lost.
- No --password flag. An argument lands in shell history, in ps output, and
  in the Docker daemon's record of the exec'd command. A TTY prompt (with
  confirmation) and --password-stdin are the two forms that avoid all three.
- Pydantic's ValidationError is never printed verbatim: its rendering embeds
  the offending value, which for a short password prints the password itself.
  Only loc and msg are shown (CLAUDE.md invariant #5).

role="admin" is recorded but nothing enforces it yet -- there is no
admin-only endpoint until invite management in Phase 1. ROLE_ADMIN/
ROLE_MEMBER become named constants, and AuthenticatedSession carries the
role for that future check. It is deliberately absent from UserOut, so no
HTTP response and no OpenAPI contract changes. The register endpoint's
password and display-name constraints move to named aliases in schemas/auth
so the CLI applies exactly the same rules rather than a drifting copy.

Verified: ruff check, ruff format --check, mypy --strict, and the full
pytest suite (28 passed) from apps/api/; `alembic check` reports no model
drift. Also smoke-tested end to end against a scratch database -- creation,
the duplicate-email refusal, and the no-TTY message all behave as described.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01R2ZKeWkZV7ehf7fivrAkkG

apps/api/velodrome/auth/service.py

@@ -23,7 +23,7 @@ from velodrome.auth.security import (
 )
 from velodrome.config import get_settings
 from velodrome.db import auth_session
-from velodrome.models import Invite, Session, User
+from velodrome.models import ROLE_ADMIN, Invite, Session, User
 
 
 class AuthError(Exception):
@@ -51,6 +51,14 @@ class AuthenticatedSession:
     user_id: UUID
     email: str
     display_name: str
+    # Carried here so the role a user actually has is available wherever identity is — an
+    # authorization check on the first admin-only endpoint (realistically invite management) is
+    # then a comparison against a value already in hand, not another query bolted on later. This
+    # is data plumbing, not an authorization mechanism: nothing reads it yet, deliberately, since
+    # there is no admin-only endpoint to protect (docs/DECISIONS.md D18). It is not a secret and
+    # is not in any response model — `schemas.auth.UserOut` deliberately doesn't declare it, so
+    # adding it here changes no HTTP response and no OpenAPI contract.
+    role: str
 
 
 async def register(
@@ -103,7 +111,58 @@ async def register(
             invite.used_count += 1
 
         return AuthenticatedSession(
-            user_id=user.id, email=user.email, display_name=user.display_name
+            user_id=user.id,
+            email=user.email,
+            display_name=user.display_name,
+            role=user.role,
+        )
+
+
+async def create_admin(*, email: str, password: str, display_name: str) -> AuthenticatedSession:
+    """Create a user with the admin role, with no invite. Operator path only — see velodrome.cli.
+
+    This is the one deliberate hole in "open signup does not exist": a fresh deployment has no
+    users and therefore nobody who can issue the first invite, so the first account has to come
+    from outside the HTTP API. It lives here rather than in cli.py because this is where
+    `auth_session` belongs (see db.py's docstring — nothing outside this module imports it), and
+    because the lookup below is exactly the pattern that module documents as safe: an exact match
+    on a unique key, never a scan.
+
+    It is not reachable over HTTP and never will be — nothing in `api/` calls it. Reaching it
+    requires the ability to run a process inside the container, which is already the ability to
+    read and rewrite the SQLite file directly, so it grants an operator-turned-attacker nothing
+    they did not already have.
+
+    Refuses outright if the email is taken, rather than updating the row — see docs/DECISIONS.md
+    D18. Creating an account and resetting an existing account's password are different operations
+    with different blast radii, and an operator re-running a bootstrap command they last ran
+    months ago means the first, never the second. The check-then-insert is safe against a
+    concurrent `register()` for the same email the same way invite redemption is: db.py issues
+    `BEGIN IMMEDIATE`, so the two transactions serialize instead of interleaving, with the unique
+    index on `users.email` as the backstop underneath that.
+    """
+    async with auth_session() as db:
+        async with db.begin():
+            existing = (
+                await db.execute(select(User).where(User.email == email))
+            ).scalar_one_or_none()
+            if existing is not None:
+                raise EmailAlreadyRegistered("an account with this email already exists")
+
+            user = User(
+                email=email,
+                display_name=display_name,
+                password_hash=hash_password(password),
+                role=ROLE_ADMIN,
+            )
+            db.add(user)
+            await db.flush()  # populate user.id before we reference it below
+
+        return AuthenticatedSession(
+            user_id=user.id,
+            email=user.email,
+            display_name=user.display_name,
+            role=user.role,
         )
 
 
@@ -140,7 +199,10 @@ async def login(
             db.add(session_row)
 
         return raw_token, AuthenticatedSession(
-            user_id=user.id, email=user.email, display_name=user.display_name
+            user_id=user.id,
+            email=user.email,
+            display_name=user.display_name,
+            role=user.role,
         )
 
 
@@ -184,7 +246,10 @@ async def validate_session(raw_token: str) -> AuthenticatedSession:
                 )
 
         return AuthenticatedSession(
-            user_id=user.id, email=user.email, display_name=user.display_name
+            user_id=user.id,
+            email=user.email,
+            display_name=user.display_name,
+            role=user.role,
         )