docs(files): document filestash across plan/README/deploy skill

Fold files./filestash into the docs that carry the service list, the vhost
map and the deploy procedure — README stack table, 00-overview, 02-caddy,
12-build-order, 14-deploy, and the deploy skill.

Two real gaps the filestash deploy exposed, now guardrails in the skill:
- update-all.sh never touches host nginx, so a NEW SUBDOMAIN silently 404s
  after deploy. It needs issue-letsencrypt.sh + render-nginx.sh --install.
- a new service with ${FOO:?} guards fails the WHOLE compose file, so a
  missing .env var means `up` starts nothing — and --hard has already run
  `down`. Check the host's .env BEFORE tearing the stack down.

Also: filestash/config.json is a single-file bind mount re-rendered every
run, so a rolling update-all leaves it on a stale inode (same trap as the
caddy conf) — force-recreate after any FILES_* change.

Correct the cochi divergence section: `git diff HEAD` on the host is now
empty (verified this deploy — the ff-pull succeeded). The documented
docker-compose.yml/package.json divergence was converged; only untracked
dnsmasq/, caddy-root-ca.crt and a stale pack/ remain. The stash-pull-pop
procedure it prescribed is no longer needed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plan/00-overview.md

@@ -13,9 +13,10 @@ Everything is driven by one env var in `.env`:
 BASE_DOMAIN=ulicraft.net      # all services are subdomains of this
 ```
 
-`render-config.sh` substitutes **only** `${BASE_DOMAIN}` into the templates.
+`render-config.sh` substitutes `${BASE_DOMAIN}` into the templates (plus the
+derived `REGISTRATION_*` and `FILES_*` values — see `20-files.md`).
 DNS is **not** this repo's concern: point `${BASE_DOMAIN}` and all subdomains
-(`auth.` `avatar.` `status.` `distribution.` `www.`) at the host running
+(`auth.` `avatar.` `status.` `files.` `distribution.` `www.`) at the host running
 nginx; that is configured outside this repo.
 
 ## Subdomain / ingress map
@@ -25,6 +26,7 @@ ulicraft.net               → nginx → caddy → landing page (/srv/www) + /la
 auth.ulicraft.net          → nginx → caddy → drasl:25585   (auth web UI + Yggdrasil API)
 avatar.ulicraft.net        → nginx → caddy → nmsr:8080      (skin/avatar renderer)
 status.ulicraft.net        → nginx → caddy → uptime-kuma:3001 (status page)
+files.ulicraft.net         → nginx → caddy → filestash:8334 (player file share, shared login)
 distribution.ulicraft.net  → nginx → caddy → /srv/distribution (static, another repo)
 mc.ulicraft.net:25565      → minecraft                      (raw MC protocol, not HTTP)
 ```
@@ -90,8 +92,8 @@ UP:
 ```
 
 Bring-up is a single command. There are no run modes and no override compose
-files — one `docker-compose.yml` holds drasl, minecraft, mc-backup, caddy, nmsr
-and uptime-kuma.
+files — one `docker-compose.yml` holds drasl, minecraft, mc-backup, caddy, nmsr,
+mc-status, uptime-kuma and filestash.
 
 ## Why each hard call was made
 
@@ -119,6 +121,9 @@ and uptime-kuma.
 │   ├── config.toml.tmpl         # render-config.sh source
 │   └── config.toml              # generated (gitignored)
 ├── nmsr/                        # avatar renderer config + Dockerfile context
+├── filestash/
+│   ├── config.json.tmpl         # render-config.sh source (files. share)
+│   └── config.json              # generated, mounted :ro (gitignored — holds hashes)
 ├── docker/nmsr/                 # nmsr image build context
 ├── server-mods/                 # filtered server modset (synced, gitignored)
 ├── launcher/                    # vendored Fjord launcher releases (gitignored)
@@ -145,9 +150,11 @@ and uptime-kuma.
 - `15-letsencrypt.md` — Let's Encrypt (OVH DNS-01) + host nginx ingress
 - `17-mod-shortlist.md` — kitchen-sink gap doc + landing mod-list dataset (PLANNED)
 - `18-landing-rework.md` — join flow / rosters / account / mod list / footer (PLANNED)
-- `19-routes.md` — HTTP route reference (nmsr / landing / auth + internal)
+- `19-routes.md` — HTTP route reference (nmsr / landing / auth / files + internal)
+- `20-files.md` — Filestash player file share (`files.`, one shared login)
 
 ## Boot/dependency order
 
 `caddy` (aliases) → `drasl` → `minecraft` (depends on drasl) → `mc-backup`.
-`nmsr` and `uptime-kuma` are always-on and join `mcnet`.
+`nmsr`, `mc-status`, `uptime-kuma` and `filestash` are always-on and join `mcnet`
+(no ordering constraints — none of them are on the auth/boot path).