fix: auth review fixes — token revocation, WS auth, seeding, and hardening

Refresh/logout and token robustness
- drop the post-rotation refresh_tokens row delete in auth_refresh so
  logout blacklists the current (rotated) refresh token; remove the
  dead _clear_refresh_token_after_rotation helper and clear_active_refresh_token
- reject non-object JWT payloads in _extract_unverified_sub so crafted
  Authorization headers return 401 instead of crashing with 500

SQLite user store
- make builtin-admin seeding idempotent: on a concurrent first start the
  losing seeder re-checks, finds the winner, and returns instead of
  raising IntegrityError
- per-thread sqlite connections + busy_timeout so Flask worker threads
  don't hit cross-thread ProgrammingError / SQLITE_BUSY
- add LogsDirectory + /var/log/vacuum-wall to ReadWritePaths in both
  systemd units so the fallback admin password actually lands on disk

Frontend
- skip apiFetch 401-recovery for public auth endpoints so a failed
  login no longer logs out a valid session
- add /passkeys to the nav (passkey registration was unreachable);
  remove the dead checkWebAuthnCapable export
- drop the CSP-blocked inline WS-URL script and the
  __WS_URL_PLACEHOLDER__ plumbing; the WS URL is derived from location

Daemon / WS
- parse Sec-WebSocket-Protocol manually (web.Request.get_subprotocols
  does not exist in aiohttp 3.13); X-Auth-Token is a custom-nginx
  fallback only — docstring and security docs corrected

Install / system
- bootstrap_auth.py is now idempotent: preserves existing auth config
  and syncs the admin password on re-runs (new reset_password helper)
- WebUI server block renders auth_basic off (the UI is JWT-protected)
- install.sh chown/chmod skips .git to avoid git dubious-ownership
  breakage
- tolerate unreadable /etc/wireguard during system import

Contracts / docs
- create_user returns 409 on duplicate username per docs/api.md
- correct docs/api.md response shapes, docs/security.md blacklist
  cleanup wording + one-refresh-per-user caveat, stale WS-URL
  references, and the .htpasswd description

Tests: +7 regression tests (rotation/logout revocation, crafted-token
401, concurrent seeding); placeholder-substitution tests replaced with
serve-as-is SPA root tests.

webui/static/hoover/components/auth.js

@@ -11,7 +11,6 @@
  *   - WebAuthn (passkey) ceremony helpers — not state management
  */
 
-import { apiFetch } from '../api.js';
 import { modelFetch } from '../model.js';
 import { getAuthData } from '../auth_model.js';
 
@@ -65,20 +64,6 @@ export function webauthnSupported() {
     return typeof window !== 'undefined' && !!window.PublicKeyCredential;
 }
 
-/**
- * Check if WebAuthn is enabled and available on the current domain.
- * Calls GET /api/auth/webauthn/capable to query the server.
- *
- * @returns {Promise<object>} { enabled, rp_id, rp_name, origin, reason? }
- */
-export async function checkWebAuthnCapable() {
-    const result = await apiFetch('/api/auth/webauthn/capable');
-    if (!result.ok) {
-        return { enabled: false, reason: 'Unable to check WebAuthn capability' };
-    }
-    return result.data || { enabled: false, reason: 'Server returned no data' };
-}
-
 /* ─── Base64url helpers ──────────────────────────────────────────────── */
 
 /**