GHSA-92hr-gmr6-h8cp

Fix: PR #7906 (ether/etherpad). A set of medium/low hardening fixes: - **Weak RNG for tokens (CWE-330):** author/session/readonly IDs were generated with `Math.random()` (client and server). Now use `crypto.getRandomValues`. - **Login timing / no failure delay (CWE-208/CWE-307):** the OIDC interaction login used a non-constant-time password compare with no failure delay. Now uses `crypto.timingSafeEqual` plus a uniform failure delay; user lookup is own-property only. - **Plugin dependency path handling (CWE-22):** plugin dependency names from package.json were used to build filesystem paths without validation (admin-gated install). Now validated against the npm name grammar. - **API parameter pollution (CWE-235):** `/api/2` merged all request headers into the API field set. Now forwards only `authorization`, matching the openapi.ts handler. - **Pad-creation side effect:** `API.appendChatMessage` could create arbitrary pads (missing `getPadSafe`). Now requires the pad to exist. - **Error info disclosure (CWE-209):** the admin file server echoed filesystem error detail; now returns a generic message.