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.

docs/api.md

@@ -206,7 +206,13 @@ Create a new user with password and per-subsystem permissions.
 | `password` | `string` | Yes | Plain-text password |
 | `permissions` | `object` | No | Per-subsystem permissions (`{ subsystem: "read" \| "rw" }`) |
 
-**Response:** `data` is `null` on success.
+**Response (`data`):**
+
+| Field | Type | Description |
+|---|---|---|
+| `id` | `int` | User ID |
+| `username` | `string` | Username |
+| `permissions` | `object` | Per-subsystem permissions (`{ subsystem: "read" \| "rw" }`) |
 
 Returns HTTP `409` if username already exists.
 
@@ -226,7 +232,13 @@ Update user's permissions. (To change a password, use `POST /api/auth/password`.
 |---|---|---|---|
 | `permissions` | `object` | No | New per-subsystem permissions |
 
-**Response:** `data` is `null` on success.
+**Response (`data`):**
+
+| Field | Type | Description |
+|---|---|---|
+| `id` | `int` | User ID |
+| `username` | `string` | Username |
+| `permissions` | `object` | Per-subsystem permissions (`{ subsystem: "read" \| "rw" }`) |
 
 Returns HTTP `404` if user not found.
 
@@ -240,7 +252,7 @@ Delete a user and all associated permissions and WebAuthn credentials (CASCADE).
 
 **Auth:** `auth: "rw"` required. Cannot delete self.
 
-**Response:** `data` is `null` on success.
+**Response:** `data` is `{"ok": true}` on success.
 
 Returns HTTP `404` if user not found.