fix: surface NIP-07 signature wait as a distinct upload phase

Episode uploads that looked 'stuck uploading to blossom' were actually
stuck waiting on the browser nostr extension's own approval popup —
confirmed via server/blossom logs showing zero incoming requests for
the reported attempt, meaning the upload never left the browser.

The UI flipped to phase 'uploading' (0%) before the NIP-07 signEvent()
call resolved, so a user who didn't notice the extension's popup saw a
progress bar frozen at 0% with no indication anything needed their
action. Added a 'signing' phase with an explicit message telling them
to check for the popup.

frontend/src/lib/blossom.ts

@@ -24,7 +24,12 @@ export async function uploadToBlossom(
   file: File,
   sha256: string,
   onProgress?: (frac: number) => void,
+  onSigning?: () => void,
 ): Promise<BlossomUpload> {
+  // signEvent() waits on the NIP-07 extension's own approval popup, which can
+  // take an unbounded amount of time (or go unnoticed) — tell the caller so
+  // the UI doesn't say "Uploading… 0%" while nothing has actually started.
+  onSigning?.();
   const now = Math.floor(Date.now() / 1000);
   const auth = await nip07().signEvent({
     kind: 24242,

frontend/src/views/wizard/EpisodeWizard.vue

@@ -17,7 +17,7 @@ const podcast = ref<PodcastSummary | null>(null);
 const creatingNew = ref(false);
 
 const file = ref<File | null>(null);
-const phase = ref<'idle' | 'hashing' | 'uploading' | 'registering'>('idle');
+const phase = ref<'idle' | 'hashing' | 'signing' | 'uploading' | 'registering'>('idle');
 const progress = ref(0);
 const error = ref('');
 
@@ -31,6 +31,7 @@ const episodeUrl = ref('');
 const phaseLabel = computed(() => ({
   idle: '',
   hashing: 'Computing sha256…',
+  signing: 'Waiting for your nostr extension to approve the upload — check for a popup (it may be behind this window).',
   uploading: `Uploading to Blossom… ${(progress.value * 100).toFixed(0)}%`,
   registering: 'Publishing episode…',
 }[phase.value]));
@@ -72,9 +73,17 @@ async function publish() {
     durationSecs.value = await probeDuration(file.value);
     const sha = await sha256File(file.value);
 
-    phase.value = 'uploading';
     const blossomUrl = settings.public!.blossomUrl;
-    await uploadToBlossom(blossomUrl, file.value, sha, (f) => (progress.value = f));
+    await uploadToBlossom(
+      blossomUrl,
+      file.value,
+      sha,
+      (f) => {
+        phase.value = 'uploading';
+        progress.value = f;
+      },
+      () => (phase.value = 'signing'),
+    );
     uploaded.value = { sha256: sha, size: file.value.size };
 
     phase.value = 'registering';