API: /accounts/profile returns null KDF for Argon2id accounts authenticated via OAuth2 client_credentials (API key)

### Steps To Reproduce

1. On a Bitwarden Cloud account, set master-password KDF to Argon2id
(Account Settings → Security → Master Password → Encryption Settings).
Example: memory=64 MiB, iterations=4, parallelism=8.

2. Obtain an OAuth2 access token via the API key flow:

curl -X POST https://identity.bitwarden.com/connect/token \
-H "Bitwarden-Client-Name: cli" \
-H "Bitwarden-Client-Version: 2026.4.1" \
-H "Device-Type: 21" \
-H "Device-Identifier: $(uuidgen)" \
-H "Device-Name: curl-test" \
--data-urlencode grant_type=client_credentials \
--data-urlencode client_id="user." \
--data-urlencode client_secret="" \
--data-urlencode scope=api \
--data-urlencode deviceType=21 \
--data-urlencode deviceIdentifier="$(uuidgen)" \
--data-urlencode deviceName=curl-test

3. Call /accounts/profile with the returned access_token:

curl https://api.bitwarden.com/accounts/profile \
-H "Authorization: Bearer " \
-H "Bitwarden-Client-Name: cli" \
-H "Bitwarden-Client-Version: 2026.4.1" \
-H "Device-Type: 21" \
-H "Device-Identifier: " \
-H "Device-Name: curl-test"

### Expected Result

Response includes the account's actual KDF settings, e.g.:

{
"kdf": 1,
"kdfIterations": 4,
"kdfMemory": 64,
"kdfParallelism": 8,
"email": "user@example.com",
...
}

(kdf: 1 = Argon2id per the KdfType enum)

### Actual Result

{
"kdf": null,
"kdfIterations": null,
"kdfMemory": null,
"kdfParallelism": null,
"email": "user@example.com",
...
}

All four KDF fields are null. Other profile fields (email, name, etc.) populate
normally.

### Screenshots or Videos

_No response_

### Additional Context

Downstream impact (add to description or "additional context"):
bw CLI 2026.3.0 and 2026.4.1 (bitwarden-cli-bin AUR + @bitwarden/cli on npm)
cannot derive the master key after `bw login --apikey`. `bw unlock --raw`
returns an 88-char session token, but every subsequent vault command
(`bw status`, `bw list items`, etc.) sees `kdfType: null` in local state,
treats the vault as locked, and falls back to the interactive master-password
prompt — which also fails since KDF is unknown. Effectively makes the
API-key auth path unusable on Argon2id accounts.

Same account works correctly on web vault, Desktop, and mobile clients;
those use the `password` grant type which appears to return KDF normally.

Reproduces identically on Arch Linux and macOS, on two physically separate
machines, with both pkg-bundled and npm-installed bw clients. Full local-state
wipe (`~/.config/Bitwarden CLI/`) + API key rotation + re-login does not
change the behavior — narrowing it to server-side, specific to the
client_credentials grant + Argon2id account combination.

### Build Version

Bitwarden Cloud (N/A)

### Environment

Cloud (bitwarden.com)

### Environment Details

- Bitwarden Cloud: identity.bitwarden.com / api.bitwarden.com (US region)
- Account KDF: Argon2id (memory=64 MiB, iterations=4, parallelism=8)
- 2FA: WebAuthn (YubiKey) — note: API key login does authenticate successfully,
so the token flow itself is fine; the regression is the profile response.
- Affected clients:
- bw CLI 2026.4.1 (bitwarden-cli-bin AUR, prebuilt pkg-bundled binary)
- bw CLI 2026.3.0 (same source, prebuilt)
- bw CLI 2026.4.1 (@bitwarden/cli npm, system Node.js)
- Affected hosts: Arch Linux (kernel 7.0.9) and macOS
- Date observed: 2026-05-18

### Issue Tracking Info

- [x] I understand that work is tracked outside of Github. A PR will be linked to this issue should one be opened to address it, but Bitwarden doesn't use fields like "assigned", "milestone", or "project" to track progress.

Start by tracing the /accounts/profile endpoint and comparing its response for password-grant and client_credentials authentication with an Argon2id account. Reproduce the supplied API-key flow, then follow the profile mapping and existing API tests; done means all four KDF fields contain the account settings and the affected CLI can derive and use the master key.

Written by the indexing model from the issue text.