Admin page laid out as a feed's settings are (#414)

Prototype for approval on the issue; not to be merged until then.

The page had grown one captioned box at a time: at 390 px the tabs ran off
the edge and hid Log, Server was eleven full-width boxes (1150 px wide on a
desktop for a one-digit number) with units and the meaning of 0 in the
labels, and Directory's Save sat between its settings and the lists below.

Each tab is now named parts in .fsec, the layout #290 gave a feed's settings,
with its switches, numbers with their unit after the box, Server's Save
sticky and greyed until a change, the tabs in their own row on a phone, the
Proxy tag by the account's name, and the log's explanation moved into each
source tab's tooltip.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RqkrVDqdiQEMWAkNGQ2tYA

web/CHANGELOG.md

@@ -17,6 +17,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - iPX opens and reads without a connection: the lists it has fetched (All Subscriptions, Unread and the feeds it preloads or you opened) are kept on the device with the pictures in their unread items, up to 200 MB of them, and items read or flagged and places in an episode while offline are sent when the connection is back. Signing out clears it all (#389).
 - An open page, or the home-screen app, takes up a new version of iPX by itself once it reconnects after a deploy, back on the item you had open; while something is playing, a dialog is open or a search is typed, it offers a reload instead (#388).
 
+### Changed
+
+- The admin page is laid out as a feed's settings are: each tab in named parts, numbers with their unit beside them, switches for on and off, Server's Save always in reach, and on a phone the tabs in a row of their own so all four fit (#414).
+
 ### Fixed
 - Swiping, or j, through more than 50 items no longer stops at the 50th until a reload: the next ones are fetched as you near the end, and Load more on the Unread tab no longer skips as many unread items as you had read (#383).
 - On the Unread tab, a short list read through no longer asks the server for more that is not there, or shows a count of 0 items beside the items still on screen (#385).