LabLink v2.1.3 - Bench Work

Bench work. Everything here came from running the client against a real
Raspberry Pi with a B&K Precision 1685B and 9205B attached, and most of it
would not have been found any other way.

✨ Added

• The bench survives a restart. The equipment list lived only in memory, so
  every container restart emptied it -- and an upgrade restarts containers. The
  server now records what it has identified in data/equipment_inventory.json
  on the docker volume, and lists those alongside the instruments it currently
  holds open. Identity is remembered; connections are not, so nothing opens a
  port at boot and an instrument someone else is using is listed rather than
  seized. This matters most for a 1685B, which does not answer *IDN? at all:
  rediscovery means inferring it from a USB serial bridge, and two bridges look
  alike.
• Min/Max tracking on the Control tab, which is how a transient the live
  number skips past gets noticed. It prints to the resolution the instrument
  actually reports.
• Auto Range for the analog and graph modes. A 5 A supply sitting at 0.3 A
  uses a sixteenth of the dial, where a 10 mA change moves the needle about a
  pixel. The scale grows to fit what has been seen and holds there rather than
  falling back as the reading drops, which made a steady supply look like a
  climbing one.
• The update warns what it will interrupt, naming the instruments that are
  connected and will be dropped while the server restarts. An output left
  enabled stays enabled with nothing watching it.
• The SSH host is offered from the connection, with the SSH user remembered
  per server once an update has worked.

🐛 Fixed

• Selecting equipment silently dropped the reading rate to 1 Hz while the
  control still read 10 Hz. It restarted the timer at a hardcoded interval; a
  display that disagrees with the behaviour is worse than either being wrong.
  The rate is also remembered between sessions now.
• The version and branch pickers could not see anything new. Both listed
  only what the clone already had, so a release or a commit pushed five minutes
  earlier never appeared however many times Refresh was pressed. They fetch on
  the button now -- and only on the button: fetching on the five-second
  refresh, which is what the first attempt did, hitched the window every few
  seconds.
• Connecting to an instrument failed with 'Equipment' object has no attribute 'resource_string'. The client model calls it resource_name;
  the code asked for the server's spelling. It had been hidden behind a 404
  storm that kept the connect task from ever being entered.
• The Control tab polled instruments the server had not opened, 404ing at
  the reading rate.
• A background refresh raised modal error dialogs from a five-second timer,
  interrupting the operator to report something unactionable -- and during an
  update not even a fault, since the server is down because we asked it to be.

📝 Changed

• The analog display is a panel meter now, after a Simpson Model 29: a
  shallow arc with the pivot low in the case, which spreads the scale over the
  full width and gives far more travel per unit than a round dial in the same
  box. It fills the window like the other two modes, where it used to sit at
  its minimum with room to spare. The case follows the theme -- grey bezel in
  both, cream card and black pointer in light, black card and green pointer in
  dark -- with the graduations and lettering printed in the same ink as the
  pointer.
• The update log fills the window instead of staying ten lines tall with a
  third of the screen empty beneath it.