v0.8.1: add ISO by URL, zero-touch admin bootstrap

Ease-of-use pass inspired by Bootimus (Dnsmasq-PXE is a manual dnsmasq
setup guide — nothing to adopt; OpenPXE already replaces that stack).

Add ISO by URL:
- New http-api `fetch` module: a small FetchJobs registry + a background
  streaming download (reqwest) that pipes a remote .iso through the same
  UploadHandle + introspection path as an upload, so a URL-fetched image
  classifies and gains boot entries identically. Progress is polled by the
  Storage view and rendered as rows, mirroring uploads.
- Routes POST/GET/DELETE /api/isos/fetch. http/https only; .iso-only
  filename derived from Content-Disposition / URL basename with path
  traversal stripped; 16 GiB cap; cancel; credential-stripped URL display.
  Operator-gated, no boot-time outbound — offline boot is untouched.
- Storage upload card gains an "Or add by URL" field with progress + cancel.

Zero-touch admin bootstrap:
- OPENPXE_ADMIN_USERNAME + OPENPXE_ADMIN_PASSWORD (or _PASSWORD_FILE for
  Docker/K8s secrets) auto-create the admin on first run, so a fresh
  container is usable with no setup wizard. Seeds the first run only — a
  lingering env var can't reset a rotated password.

Tests: URL parse / filename / Content-Disposition unit tests + a wiremock
end-to-end fetch-into-store integration test. clippy/fmt/node clean.

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

crates/http-api/src/app.rs

@@ -94,6 +94,17 @@ pub fn build_router(state: AppState) -> Router {
         // JSON API.
         .route("/api/isos", get(api_list_isos).post(api_upload_iso))
         .route("/api/isos/{id}", delete(api_delete_iso))
+        // v0.8.1: add ISO by URL — server-side streaming download + progress
+        // polling. Static `fetch` coexists with `{id}` above (matchit
+        // prioritizes the literal), same as `/api/queue/join` vs `{entry_id}`.
+        .route(
+            "/api/isos/fetch",
+            get(crate::fetch::api_iso_fetch_list).post(crate::fetch::api_iso_fetch_start),
+        )
+        .route(
+            "/api/isos/fetch/{id}",
+            delete(crate::fetch::api_iso_fetch_cancel),
+        )
         .route("/api/uploads", post(api_upload_begin))
         .route(
             "/api/uploads/{upload_id}",
@@ -1857,6 +1868,12 @@ async fn api_docs() -> Json<serde_json::Value> {
                      "summary": "Clear an ISO's boot password."},
                     {"method": "PUT", "path": "/api/isos/{id}/category",
                      "summary": "Set the menu category. Body: { \"category\": \"os\" | \"tools\" }."},
+                    {"method": "POST", "path": "/api/isos/fetch",
+                     "summary": "Add an ISO by URL. Body: { \"url\", \"filename\"? }. The server streams the .iso into storage and introspects it. Returns { fetch_id }."},
+                    {"method": "GET", "path": "/api/isos/fetch",
+                     "summary": "Poll URL-fetch progress — [{ id, filename, url, downloaded, total, state }]. Completed jobs are returned once."},
+                    {"method": "DELETE", "path": "/api/isos/fetch/{id}",
+                     "summary": "Cancel an in-flight URL fetch, or dismiss a finished/failed one."},
                 ],
             },
             {