feat(deploy): halkyon.li's first start, its .env made on the host (ADR 0039, D21)

first-start.md takes the instance from a bare host to running, once: the
sidecars' users, deploy with a read-only key to the forge and the
developer's keys (GPG for redeploy.sh's check, SSH pinned to it), .env,
SimpleLogin's app, the sidecars' folders and Jellyfin moved in, a role and
database for each app's server, the first start, the first operator by
ADR 0021's SQL, and the backups.

halkyon-li-env.sh writes .env with every secret made on the host and never
over an existing file, as the peppers must not change once people sign in:
SimpleLogin alone with approval, everything running behind the forward,
Train's map and routes over southern Bavaria and its search over Germany
until the Instance console cuts regions, Germany as where data and backups
are.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/host/README.md

@@ -182,7 +182,8 @@ for the later.
 6. **Reboot**, at home, to see each step hold: the passphrase over SSH (step 2), no
    desktop (step 3), Docker on the HDD (step 4), the tunnel up before Docker (step 5).
 
-The instance itself follows (its users, checkout, `.env` and first deploy). Then:
+The instance itself follows, once: `first-start.md` (its users, checkout, `.env`, the
+databases, the first start, the first operator, the backups). Then:
 
 7. **The CI runner in its nightly window** (D6, D16), once `deploy` and its checkout
    exist. Its user, its folder on the HDD, Forgejo's runner (v13.1.0, the version