feat(homepage): add Arbo 'Raven' theme to custom.css; correct the tab-bar note

Ports Arbo's design tokens (irv-ml1:8201) into conf/custom.css — flat raven
ink #021425, card surface #112333 on #1B2E3D borders, Manrope, and mint
#2FFC89 reserved for signal so a green pill means the service is actually
serving. Values read off Arbo's running :root custom properties rather than
sampled from a screenshot. CSS rather than settings.yaml because Homepage's
color: setting only accepts built-in Tailwind ramps.

NOT YET DEPLOYED — live still runs the stock theme pending an A/B decision.
Prototype is at 10.0.50.45:5199; shots in ~/booth-data/homepage-cleanup/.
Promoting it also means dropping the background: block from settings.yaml.

Also corrects the previous commit's tab-bar claim. It is not a fixed few
minutes of warm-up: a fresh container was still tab-less at 4m30s twice, and
recovered on its own about an hour later. Cause remains unpinned; the README
now records the measured timing and the four ruled-out causes.

stacks/homepage/README.md

@@ -84,21 +84,39 @@ Three fixes, all in this stack's config except where noted:
   `settings.yaml`. Check with `GET /api/services`, which prints live per-group
   counts.
 
-## RESOLVED — the tab bar takes several minutes to appear after a recreate
+## The tab bar goes missing after a recreate, then comes back on its own
 
-**Status: closed, and the answer is "wait".** After the 2026-08-18 recreate the
-client render came up with no tab bar, no wallpaper and no i18n (the search box
-read the raw key `search.search`); groups fell back to side-by-side columns.
-It restored itself with no further intervention. **A freshly recreated homepage
-container needs a few minutes before the client render is whole** — far longer
-than the healthcheck takes to report `healthy`, which is the trap: `docker ps`
-says the service is up while the page is still visibly wrong.
+**Status: self-healing, cause not pinned. Do not chase it.** After a recreate
+the client render comes up with no tab bar, no wallpaper and no i18n (the
+search box shows the raw key `search.search`), and groups fall back to
+side-by-side columns. It restores itself with no intervention.
 
-**So: after any `docker compose up -d --force-recreate` here, do not judge the
-dashboard for at least ~5 minutes, and do not start changing config to chase
-it.** Everything below is the evidence trail from doing exactly that, kept
-because it rules out four plausible causes and will save the next session the
-same hour.
+**Timing, measured rather than assumed:** five minutes is NOT enough — a fresh
+container was still tab-less at 4m30s, twice. It was observed healthy again
+after a gap of roughly an hour. So the window is somewhere between those, and
+`docker ps` reporting `healthy` says nothing about it: the container is
+serving, the page is just wrong.
+
+**Practical rule: recreate, then walk away and re-check later.** Do not start
+editing config to fix it — that is how an hour got spent ruling out four
+causes that were never the cause:
+
+- **Not the config.** Restoring `settings.yaml` *and* `services.yaml` to their
+  committed versions reproduces it, as does the pre-adoption backup config in
+  `/opt/docker-bu/conf/homepage/`.
+- **Not the v2.0.0 release.** A throwaway container on `v1.13.2` (the last v1)
+  shows identical symptoms, and the image never changed anyway — working and
+  broken containers both report `v2.0.0` / rev `17456f2`.
+- **Not `PUID`/`PGID`**, and not Docker discovery — tested with both, and with
+  the socket unmounted entirely.
+- **Not a server-side failure.** The server-rendered HTML still contains the
+  tab markup, the background URL and `useEqualHeights` throughout, and
+  `GET /api/validate` returns `[]`. Whatever is lost, is lost client-side, and
+  with no page error, no failed chunk and no non-200.
+
+If someone does want to pin it: the shape (recovers on a long timescale, no
+client exception) points at a cache or revalidation window rather than a
+config fault. Start there, not in this directory.
 
 **What it is not** — both obvious suspects were tested and cleared:
 
@@ -119,17 +137,32 @@ widget 403s. `GET /api/validate` returns `[]`. A fresh container never
 renders tabs here regardless of image version, config version, `PUID`/`PGID`,
 or whether Docker discovery is mounted at all.
 
-**What it actually was: warm-up time.** Every throwaway container in the list
-above was judged within ~30 seconds of starting, which is why they all looked
-broken — they were all in the same warm-up window, and that consistency read as
-a reproduction when it was really the same mistake five times. The live
-container recovered on its own once left alone. The lesson is a measurement
-discipline, not a config one, and it sits alongside the existing warning that
-`docker ps` health and a correct render are different questions.
+Every throwaway container in that list was judged within ~30s of starting, so
+they were all inside the same window — and that consistency read as a
+reproduction when it was really the same measurement mistake five times over.
+This sits alongside the existing warning that `docker ps` health and a correct
+render are different questions.
 
 Before/after evidence: `~/booth-data/homepage-cleanup/` on nh3-dev →
 `http://10.100.10.50:8090/b/homepage-cleanup/` (24h TTL).
 
+## Theme — the Arbo "Raven" palette (`conf/custom.css`)
+
+`conf/custom.css` carries a port of Arbo's design tokens (irv-ml1:8201): flat
+raven ink `#021425`, card surface `#112333` on `#1B2E3D` borders, Manrope, and
+mint `#2FFC89` reserved for signal — a status pill is green only when the
+service is actually serving. Values were read off Arbo's running `:root`
+custom properties, not sampled from a screenshot, so drift checks are a diff.
+
+It lives in CSS rather than `settings.yaml` because Homepage's `color:` setting
+only accepts built-in Tailwind ramps and has no separate surface/border/accent
+knobs. `color: slate` stays as the base ramp. The `!important` flags are
+load-bearing against Tailwind utility specificity.
+
+Pairs with removing the `background:` block from `settings.yaml` — Arbo has no
+background image, and the wallpaper fought the card surfaces, which sit only a
+little lighter than the page.
+
 ## Open question
 
 `ESH-FileBot` (`10.0.50.70`) is still described as "role TBC" — it responds to