The policy builder only offered "Matches everything" (the `true` scope node),
which also targets servers. Authoring an estate-wide policy almost always means
"every PC an operator sits at", and a reboot or script push against a server is
a materially different event.
Adds an `allpcs` scope node that matches every endpoint except those whose
computer type is server-designated. Server designation reads the computer type's
ICON slug, which is nominally a UI hint and is now load-bearing; it was chosen
over matching the type NAME (a site can rename "Server") and over a new isserver
column (needs a migration). It is isolated behind SERVER_ICON so promoting it to
a real flag later is a one-place change.
The `true` node is retained and still matches servers, so existing policies keep
their exact meaning rather than silently re-scoping. It stays visible in the
dropdown only when editing a policy that already uses it; new policies default
to `allpcs`.
Covered by tests/test_plugins/test_computers_policy_allpcs.py, verified against
a planted canary so the server-exclusion assertions are known to bite.
Default fuzzy reconcile threshold to 0 and refuse merges when digit runs differ so numbered labels like Bay 311 never bind to Bay 310. Keep edit forms from clearing saved model fields when category filtering hides untyped rows. Includes in-progress computers policy and endpoints command feature work.
