feat(admin): add OAuth scopes management page

[nshirley]

Because:

• fxa_oauth.scopes is only seeded from the OAUTH_SCOPES env var at auth-server boot, so there is no way to add or remove a scope in deployed (k8s) environments without a redeploy.
• Downstream work needs to reference scope rows by a stable numeric id and accept arbitrary scope values (including the empty string).

This commit:

• Adds patch-036-037.sql: replaces the scope PRIMARY KEY with an AUTO_INCREMENT id, keeping scope as a UNIQUE index so grant-time lookups are unchanged.
• Adds the Scope model (fxa-shared) and an OAuthScopesController at /api/oauth-scopes: GET (list), POST (create), DELETE :id. Create validates body shape and the 128-char limit, accepts any string, and maps ER_DUP_ENTRY to 409; delete returns 404 when missing.
• Adds OAuthScopes (view), CreateOAuthScope, and DeleteOAuthScope AdminPanelFeatures, gating create/delete to Admin and view to Support (mirrors the WafTokens split).
• Adds PageOAuthScopes (list, create form, per-row delete behind a confirm dialog and warning banner) plus Nav and route wiring.

Closes FXA-13786

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