Offline, a private feed without its address shows No episodes #476

A private feed opened for the first time while offline, on a device that doesn't have its address yet, shows "No episodes" instead of saying its address isn't on this device.

Reproduce (V-474, Obsidian 1.14.4, Linux, at #474's head 873e688)

1. On a second device, a synced private feed has no address yet ("Set feed address" is needed).
2. Go offline, then open that podcast.
3. It shows "No episodes". Only after reconnecting does it show "Address not on this device" with Set feed address.

The Offline strip is visible and nothing is lost, but the message is misleading. Location: src/services/FeedRepository.ts:141. The missing-address state is known locally and doesn't need the network, so it should show whether or not the device is online.

Related limits from #474, low priority:

• a request that started online before the connection dropped can be joined on reconnect, instead of starting fresh;
• an explicit URI request made offline can be joined the same way (Refresh recovers).