chore: rename project from podpuddle to podsteadr

Renames the repo directory and every podpuddle/PODPUDDLE reference
across code, config, and docs to podsteadr/PODSTEADR (package names,
Docker Compose project/service/volume names, env var names, UI/RSS
strings). Existing Docker volume data (uploaded blobs, mediamtx
recordings, the server's sqlite DB and its nostr identity key) was
migrated to new podsteadr_-prefixed volumes with matching filenames
so it isn't orphaned by the rename.

frontend/src/App.vue

@@ -16,7 +16,7 @@ async function logout() {
     <header class="border-b border-slate-200 bg-white">
       <div class="mx-auto flex max-w-4xl items-center justify-between px-4 py-3">
         <RouterLink to="/" class="flex items-center gap-2 text-lg font-bold text-puddle-700">
-          <span aria-hidden="true">💧</span> podpuddle
+          <span aria-hidden="true">💧</span> podsteadr
         </RouterLink>
         <nav v-if="auth.pubkey" class="flex items-center gap-4 text-sm">
           <RouterLink to="/" class="hover:text-puddle-600">Home</RouterLink>

frontend/src/lib/api.ts

@@ -1,4 +1,4 @@
-// Thin fetch wrapper for the podpuddle API (session cookie auth).
+// Thin fetch wrapper for the podsteadr API (session cookie auth).
 
 export class ApiError extends Error {
   constructor(public status: number, message: string) {

frontend/src/lib/blossom.ts

@@ -1,6 +1,6 @@
 // Browser-direct Blossom (BUD-02) upload: hash locally, sign the kind-24242
 // authorization with the user's NIP-07 extension, PUT straight to the blossom
-// server. The file never transits podpuddle.
+// server. The file never transits podsteadr.
 
 import { nip07 } from './nip07';
 

frontend/src/views/LoginView.vue

@@ -27,7 +27,7 @@ async function login() {
   <div class="mx-auto max-w-md">
     <div class="card text-center">
       <div class="mb-2 text-4xl" aria-hidden="true">💧</div>
-      <h1 class="mb-1 text-2xl font-bold">podpuddle</h1>
+      <h1 class="mb-1 text-2xl font-bold">podsteadr</h1>
       <p class="mb-6 text-slate-500">Publish podcasts and go live — on nostr, from your own server.</p>
 
       <template v-if="hasNip07()">