fix(settings): tell an SSO account its password lives at the identity provider (#850)

[alex-dembele]

Closes #850

An account that signs in through an identity provider has no password in OpenRisk. The Change password card used to show it three fields that could only fail: it found out after submitting, from a 409 no_local_password. The card now reads has_password from /auth/me before rendering anything.

Stacked on #848 (base: 754-…), because has_password comes from there. Once #848 is merged, GitHub retargets this PR to master.

Behaviour

/auth/me	Card
loading	skeleton, no form
has_password: false	the existing message accountSecurity.managedByIdp (FR/EN); no fields, no button, no show/hide toggle
has_password: true	the form, unchanged
read failed	the form as before; the server's 409 still switches it to the message

Changes: useHasLocalPassword() (new hook), and fetchHasLocalPassword() in authService.ts, which fetchDisableMFAProof from #754 now reuses. No new i18n key, so FR/EN parity is untouched.

Verification

$ npx vitest run src/features/auth/__tests__/changePasswordCard.test.tsx     (3 consecutive runs)
      Tests  7 passed (7)      ← 4 existing + 3 new (#850)
$ npx tsc --noEmit -p .    → OK
$ npx eslint <touched files>   → OK
$ npx vitest run src/features/auth src/features/settings src/shared
      Tests  384 passed (384)   ← 7 of 8 runs; see "Not done"

Live (branch server on PostgreSQL 16 with a fresh database, real React app on Vite, Chromium):

• Password account: the card shows its 3 password fields; no message.
• Same session after users.password = '': the card shows "Ce compte se connecte via votre fournisseur d'identité : son mot de passe se change chez lui."; 0 fields, 0 buttons, 0 requests to /auth/password/change.
• Dark theme: text #b5b2aa on build: restore green tree (build/vet/lint) + CI gate #111, about 9:1. Screenshots: .playwright-mcp/850-sso-card-light.png, 850-sso-card-dark.png.

Not done

• One run of the auth + settings + shared suites had 2 failures whose names I didn't capture. The next 7 runs (including 2 under tsc load) were all green, and the 7 card tests passed 3 times out of 3. It looks like a pre-existing timing flake, but I couldn't reproduce or name it.

🤖 Generated with Claude Code