Bring back the external API keys

Commit 0dbb13f removed the whole feature: the apikeys tab, the /ui/apikeys
routes, requireApiKey, the /api/v1 router, the ApiKey type, the better-sqlite3
dependency and UI_DB_FILE in the CLI and the installer. Only the untracked
awg-ui/API.md survived, so the README went on to claim there was no key-based
API at all.

Restores all of it: ui.db with the api_keys table, awgk_ key generation storing
only the SHA-256 and a display prefix, the JWT-guarded CRUD, and the /api/v1
router mounted before the JWT proxy on /api so the key auth is not swallowed.
The tab comes back as its own folder and the registry picks it up on its own.
UI_DB_FILE points at /etc/amnezia/amneziawg/ui.db, outside the install tree, so
reinstalling keeps the keys; a fresh install moves the old one aside with its
WAL sidecars.

better-sqlite3 takes the slot of jsonwebtoken, which arrived with the MA7
integration and has been unused since 068cab4 removed it.

One defect is not reproduced: the /api/v1 handlers called ctrl() without a
try/catch, and Express 4 does not catch async rejections, so a single request
with awg-ctrl down killed the panel process. They now answer 502 like proxy()
already did.

The API contract is documented in the README rather than linked: .gitignore
excludes every markdown but README.md, so awg-ui/API.md is not in the repo and
the link would break on a clone.

Checked against a running server: login, key create/list/delete, 400 on a bad
label, 401 without a JWT, "API key required" rather than "Unauthorized" on
/api/v1, "Invalid API key" for a deleted key, last_used updating, and all three
/api/v1 routes returning 502 with the process still alive.

awg-ui/src/tabs/apikeys/apikeys.css

@@ -0,0 +1,77 @@
+/*
+Copyright (c) 2026 Ivan Vasilev
+This source code is licensed under the MIT license found in the
+LICENSE file in the root directory of this source tree.
+*/
+/* Стили вкладки «API-ключи». Общая дизайн-система — в App.css. */
+
+/* Открытый API-ключ (показывается один раз при создании) */
+.apikey-value {
+    font-family: var(--mono);
+    font-size: 13px;
+    color: var(--on-surface);
+    background: var(--surface-container);
+    border: 1px solid var(--outline-variant);
+    border-radius: 12px;
+    padding: 12px 14px;
+    width: 100%;
+    word-break: break-all;
+    user-select: all;
+}
+
+.apikey-cards-list { display: none; flex-direction: column; gap: 12px; }
+
+.apikey-count { font-size: 12px; color: var(--neutral-text); }
+.apikey-empty {
+    font-size: 14px;
+    color: var(--neutral-text);
+    text-align: center;
+    padding: 48px 0;
+}
+.apikey-card {
+    background: var(--surface-bright);
+    border: 1px solid var(--outline-variant);
+    border-radius: var(--r-card);
+    padding: 16px;
+    display: flex;
+    flex-direction: column;
+    gap: 12px;
+}
+.apikey-card-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    gap: 8px;
+}
+.apikey-card-title {
+    display: flex;
+    align-items: baseline;
+    gap: 8px;
+    min-width: 0;
+}
+.apikey-card-num   { font-size: 12px; color: var(--neutral-dot); flex-shrink: 0; }
+.apikey-card-label {
+    font-size: 16px;
+    font-weight: 500;
+    color: var(--on-surface);
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+}
+.apikey-card-prefix {
+    font-family: var(--mono);
+    font-size: 13px;
+    color: var(--neutral-text);
+    word-break: break-all;
+}
+.apikey-card-meta {
+    display: flex;
+    justify-content: space-between;
+    gap: 8px;
+    font-size: 12px;
+    color: var(--neutral-text);
+}
+
+@media (max-width: 640px) {
+    .apikey-cards-list { display: flex; }
+}