fix!: deprecate login_type=none, convert existing users to password login (#26851)

> 🤖 This PR was modified by Coder Agents on behalf of Jake Howell.

Deprecates `login_type=none` (legacy passwordless machine users) in
favour of premium **service accounts**, and migrates existing accounts
off the deprecated path while preserving their identity. Resolves
[DEVEX-226].

## What this does

- **Creation is gated** — `POST /users` and `coder users create` reject
`login_type=none` (and the deprecated `--disable-login`) unless a
service account is requested.
- **Existing users are converted** — migration
`000554_legacy_none_login_to_password` rewrites legacy non-system,
non–service-account `login_type='none'` accounts to
`login_type='password'`. Email addresses are **preserved** and existing
API tokens remain valid. Admins can set a password if interactive login
is desired.

## Why convert to `password` and not `is_service_account`?

Migration `000433_add_is_service_account_to_users` adds two CHECK
constraints:

- `users_email_not_empty`: `(is_service_account = true) = (email = '')`
- `users_service_account_login_type`: `is_service_account = false OR
login_type = 'none'`

Turning a real, email-bearing `login_type=none` user into a service
account would require **blanking their email**. Converting to `password`
instead preserves the account and its email.

> ⚠️ **Breaking / one-way.** The `down` migration cannot restore which
users originally had `login_type='none'`.


Decision log

- **Goal:** move existing `login_type=none` users off the deprecated
path while preserving their identity/email.
- **Constraint discovered:** the `is_service_account` CHECK constraints
(migration `000433`) make a literal `none → service account` conversion
require blanking emails, so this PR converts to `password` instead to
keep emails intact.
- **Implementation:** creation-gating in `cli/usercreate.go` and
`coderd/users.go`, matching test updates, plus the
`000554_legacy_none_login_to_password.{up,down}.sql` migration.
- **CI fix:** the branch was behind `main` and its migration originally
numbered `000534`, which collided with main's
`000534_drop_chat_model_configs_provider`. Merged `main` and renumbered
to `000554` (next free after main's `000553`). `make gen` produces no
drift (the migration is data-only).



> The service-account conversion alternative (#27182, which blanked
emails) was closed in favour of this password-preserving approach.
>
> Docs follow-up: #27333.

[DEVEX-226]: https://linear.app/issue/DEVEX-226

---------

Co-authored-by: Sushant P <zenithwolf1000@users.noreply.github.com>

coderd/userauth_test.go

@@ -153,13 +153,19 @@ func TestUserLogin(t *testing.T) {
 
 	t.Run("LoginTypeNone", func(t *testing.T) {
 		t.Parallel()
-		anotherClient, anotherUser := coderdtest.CreateAnotherUserMutators(t, client, user.OrganizationID, nil, func(r *codersdk.CreateUserRequestWithOrgs) {
-			r.Password = ""
-			r.UserLoginType = codersdk.LoginTypeNone
+		client, db := coderdtest.NewWithDatabase(t, nil)
+		first := coderdtest.CreateFirstUser(t, client)
+
+		noneUser := dbgen.User(t, db, database.User{
+			LoginType: database.LoginTypeNone,
+		})
+		dbgen.OrganizationMember(t, db, database.OrganizationMember{
+			OrganizationID: first.OrganizationID,
+			UserID:         noneUser.ID,
 		})
 
-		_, err := anotherClient.LoginWithPassword(context.Background(), codersdk.LoginWithPasswordRequest{
-			Email:    anotherUser.Email,
+		_, err := client.LoginWithPassword(context.Background(), codersdk.LoginWithPasswordRequest{
+			Email:    noneUser.Email,
 			Password: "SomeSecurePassword!",
 		})
 		require.Error(t, err)