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/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';