Keep builders coming when DigitalOcean sells out a size or region (#861)

* Keep builders coming when DigitalOcean sells out a droplet size

ric1 sold out of g5-32vcpu-64gb-50gb, and every create came back 422. curl -f
dropped the reason and set -e ended the tick, so builders only appeared when
capacity happened to free up, and the journal showed nothing but "curl: (22)".

Try each of SIZES in turn, logging DigitalOcean's refusal message, and fail
the tick only when every size is refused. Builders now power off however
start.sh exits, so a failed registration is reaped instead of counting as a
booting runner until MAX_AGE_MINUTES. The controller unit pulls the checkout
before each tick, so merged controller fixes reach the box.

* Create builders in any region that has the size in stock

ric1 sold out of g5-32vcpu-128gb-50gb within minutes of the box switching to
it. Builders need nothing from a particular region, so read DigitalOcean's
size catalog once per tick and try each of SIZES in every region it lists in
stock, REGIONS first if set. A refused pair is dropped for the rest of the
tick.

ci/controller-box/controller.env.example

@@ -5,8 +5,10 @@ GITHUB_TOKEN=github_pat_...
 REPO=omacom/omarchy-pkgs
 LABEL=omarchy-builder
 TAG=omarchy-builder
-REGION=ric1
-SIZE=g5-32vcpu-64gb-50gb
+# Builder sizes, tried in order in any region that has them in stock.
+SIZES="g5-32vcpu-64gb-50gb g5-32vcpu-128gb-50gb"
+# Optional: regions to try first, e.g. "ric1". Empty means any.
+REGIONS=
 MAX_DROPLETS=6
 MAX_AGE_MINUTES=200
 LOCK=/run/omarchy-controller/lock