T10.4: remove the local password path entirely

Real deletion (D15's 'full replacement'), not a toggle. Okta is now the only
credential this app accepts anywhere.

Backend:
- server/models.py: drop User.password_hash.
- server/alembic/versions/1d60a608bb51_...: matching migration (op.drop_column,
  same plain-drop precedent as project_role/locked_until/etc.; downgrade re-adds
  it with server_default='').
- server/auth.py: remove hash_password/verify_password/password_problem/
  MIN_PASSWORD_LEN/_COMMON_PASSWORDS, create_reset_token/decode_reset_token/
  RESET_MINUTES, the bcrypt import. Roles/tokens/cookies/get_current_user
  untouched.
- server/app.py: remove login(), the whole self-service reset-password block
  (forgot-password/reset-available/reset-password), and change_password()
  (POST /api/auth/password). Rework create_user() to drop the password field
  (with a docstring note: the username must exactly match the eventual Okta
  identity claim, or a later sign-in provisions a second account instead of
  matching this one). Remove admin_reset_password() outright - nothing left to
  reset. Fixes a bug this task's own predecessor left behind: okta_callback()'s
  JIT provisioning (T10.3) was still setting password_hash="", which would have
  raised TypeError the moment the column was actually dropped.

Admin bootstrap (D16): server/manage_users.py moves from creating accounts
(create/create-admin/reset-password, all password-based) to a single 'promote
<username> --role <role>' command that changes the role on a row Okta's JIT
provisioning already created - the documented path for naming the first admin.
list/disable/enable unchanged.

Frontend: html/users.js drops the password field and validation from
createUser(), removes resetPw() and its button (nothing left to reset).
html/users.html drops the #nu-password input, adds a tooltip on username
explaining the exact-match-to-Okta requirement. html/auth-guard.js removes the
wpChangePassword dialog; html/wp-sidenav.js removes the 'Password' menu item
that opened it.

Tests: tests/browser_check.py and tests/launcher_check.py stop hashing a
password to seed fixture rows (and the --keep-server hint now prints a
ready-to-use cookie-setting snippet instead of a dead username/password).
tests/pipeline_check.py and tests/token_check.py drop an unused PW import.
tests/console_dialogs_check.py: the admin password-reset dialog it drove no
longer exists, so that scenario is removed - the prompt-with-validate() UI
pattern it exercised is still covered via creator_dialogs_check.py's
wp-creation-app.js call sites, noted in this file's docstring so the coverage
move isn't silent. tests/url_state_check.py: the "next= survives a real sign-in
via login" scenario is explicitly marked SKIPPED (not deleted, not faked) -
that promise is specific to the login FORM this task removed and can't be
honestly re-proven until T10.5 rebuilds it as an Okta redirect; a minted-token
cookie now stands in as setup only, so scenarios 3-6 in that file still get a
signed-in page to run against.

server/smoketest.py and server/seed_demo.py: switched from POST /api/auth/login
to minting a session the same way okta_callback() does (auth.create_token(),
seeded into the cookie jar) rather than waiting on T10.7. This is a real
operational change, documented in both files' own AUTHENTICATION sections: they
now need to run where AUTH_SECRET_KEY and the database match the target
server's (inside the api container, or local dev) - they can no longer sign in
to an arbitrary remote URL from an unrelated workstation, because Okta requires
a real browser and these are stdlib scripts. The account must already exist;
neither script creates or promotes one.

server/requirements.txt: bcrypt dropped, nothing imports it anymore.

Verified: full Alembic chain (baseline through this migration) upgrades and
downgrades cleanly against a throwaway SQLite DB. okta_callback() JIT
provisioning re-tested against the post-migration schema (would have thrown
before the password_hash="" fix above). create_user() verified via a live HTTP
call with no password field. manage_users.py promote verified end to end
(seed a JIT-shaped row at project_user, promote to admin, list). smoketest.py
and seed_demo.py both run to completion against a live uvicorn instance using
the new minted-session path - 25/25 checks, including logout actually
invalidating the session (proving the cookie-jar seeding didn't just fake the
sign-in, it preserved the real expiry mechanics).

wave-10.md T10.4 / D15 / D16

server/models.py

@@ -142,8 +142,10 @@ class WorkPackage(Base):
 
 
 class User(Base):
-    """A login account. Passwords are never stored in the clear — only a bcrypt
-    hash (see server/auth.py). `username` is what people sign in with.
+    """A login account. No password is stored here or anywhere else — identity is
+    confirmed by Okta (OIDC), this app only decides what the account may do once
+    Okta has vouched for it (see server/okta_auth.py, server/auth.py, D15/D16).
+    `username` is what Okta's identity claim resolves to.
 
     Two independent notions of "role", deliberately separate:
       • role          the PERMISSIONS role — what the account may do in the app.
@@ -159,7 +161,6 @@ class User(Base):
     username: Mapped[str] = mapped_column(String(120), unique=True, index=True)
     email: Mapped[str] = mapped_column(String(200), default="")
     full_name: Mapped[str] = mapped_column(String(200), default="")
-    password_hash: Mapped[str] = mapped_column(String(200), default="")
     role: Mapped[str] = mapped_column(String(20), default="project_user")  # permissions role
     # Job function on the project — free text, offered from a suggested list.
     project_role: Mapped[str] = mapped_column(String(120), default="")