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.

lib/auth.py

@@ -217,19 +217,6 @@ def blacklist_active_refresh_token(username: str) -> None:
     db.run(Q_DELETE_REFRESH_TOKEN, (username,))
 
 
-def clear_active_refresh_token(username: str) -> None:
-    """Remove the user's stored refresh token entry without blacklisting.
-
-    Used when the refresh token has already been blacklisted (e.g., during
-    a successful refresh rotation).
-
-    Args:
-        username: The username.
-    """
-    db = get_db()
-    db.run(Q_DELETE_REFRESH_TOKEN, (username,))
-
-
 def _extract_unverified_sub(token_string: str) -> str | None:
     """Extract the ``sub`` claim from a JWT payload without signature verification.
 
@@ -254,6 +241,8 @@ def _extract_unverified_sub(token_string: str) -> str | None:
             payload_b64 += "=" * padding
         payload_json = base64.urlsafe_b64decode(payload_b64)
         payload = json.loads(payload_json)
+        if not isinstance(payload, dict):
+            return None
         return payload.get("sub")
     except (ValueError, json.JSONDecodeError, UnicodeDecodeError):
         return None