v0.5.0: Wake-on-LAN, webhook notifications, Advanced tab, login logo, update check

Closes the v0.4.x chapter — NFS works end to end. Five additions:

## Wake-on-LAN (Hosts → Bound hosts)
- New core::wol module: parse any MAC form, build the 102-byte magic
  packet, broadcast it. No special capability needed (ephemeral source
  port; SO_BROADCAST). Sends to the limited broadcast (255.255.255.255)
  AND the server's own subnet broadcast (computed from advertised IP +
  detected mask) so it reaches the right VLAN.
- POST /api/hosts/:mac/wol — only fires for *bound* MACs (404 otherwise)
  so it's not an open packet sprayer.
- Bound-hosts table grows a "Wake" button with inline Waking…/Sent ✓
  state.

## Webhook notifications (Advanced tab)
- core::notify: NotifyConfig + NotifyStore (notify.json), one provider
  at a time — Slack / Discord / Teams (incoming-webhook JSON) or SMTP.
  SMTP password is persisted but redacted on GET behind a __keep__
  sentinel the UI round-trips so the secret never leaves the box.
- http-api::notify: delivery — reqwest POST for chat (provider-shaped
  bodies), lettre for SMTP (rustls, STARTTLS/implicit TLS, no plaintext).
  10s timeout; every send is best-effort.
- GET/PUT /api/notify, POST /api/notify/test.
- Fired fire-and-forget on the canonical "machine is imaging" boot event
  and on WoL — never blocks the boot path.

## UI: Advanced tab
- New nav item. Holds the webhook config card and the API reference
  block (relocated from the bottom of Settings).

## UI: login/setup logo (FleetDM treatment)
- /api/me now returns has_custom_logo + logo_rev (public bootstrap).
  The login, setup, and connection-error cards render the uploaded logo
  full-width with the "OpenPXE" wordmark dropped — matching the sidebar.

## About: update check + licenses
- "Check for updates" button → GET /api/updates/check queries the Gitea
  releases API (derived from CARGO_PKG_REPOSITORY) and compares to the
  running version. Strictly on-demand — no background polling, keeps the
  air-gapped promise.
- License card documents the MIT OR Apache-2.0 dual license with links,
  plus a note on bundled components (iPXE GPLv2/UBDL, samba, wimtools).

Deps: lettre (SMTP, rustls) + reqwest gains the json feature. Both
rustls so the static musl binary stays OpenSSL-free.

Tests: 179 passing (+notify round-trip/redaction, webhook validation,
WoL-unbound-404, WoL packet loopback, version-compare). clippy clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

crates/http-api/src/auth.rs

@@ -303,12 +303,20 @@ pub async fn api_logout(
 /// * `authenticated: false` — admin exists, no session; show login.
 /// * `authenticated: true` + `user` — let the dashboard load.
 pub async fn api_me(State(state): State<AppState>, headers: axum::http::HeaderMap) -> Response {
+    // v0.5.0: include branding bootstrap so the pre-auth login/setup
+    // screens can render the FleetDM-style full-width custom logo (and
+    // cache-bust it) without an extra round trip. `/api/me` is public,
+    // and the logo asset is public, so this leaks nothing sensitive.
+    let has_custom_logo = state.branding.has_logo();
+    let logo_rev = state.branding.logo_rev();
     if !state.admin.is_configured() {
         return (
             StatusCode::OK,
             Json(json!({
                 "setup_required": true,
                 "authenticated": false,
+                "has_custom_logo": has_custom_logo,
+                "logo_rev": logo_rev,
             })),
         )
             .into_response();
@@ -323,6 +331,8 @@ pub async fn api_me(State(state): State<AppState>, headers: axum::http::HeaderMa
                 "authenticated": true,
                 "user": state.admin.snapshot(),
                 "session_user": u,
+                "has_custom_logo": has_custom_logo,
+                "logo_rev": logo_rev,
             })),
         )
             .into_response(),
@@ -331,6 +341,8 @@ pub async fn api_me(State(state): State<AppState>, headers: axum::http::HeaderMa
             Json(json!({
                 "setup_required": false,
                 "authenticated": false,
+                "has_custom_logo": has_custom_logo,
+                "logo_rev": logo_rev,
             })),
         )
             .into_response(),