Rename SUBSD_* env vars to SUBS_* to match upstream refactor

The upstream SpacesOps app refactored its SUBSD_* environment variables to
SUBS_* (verified against server.js in spacesops/spacesops:v1.0.0). Update the
package to match so the configured values reach the app:

- main.ts: inject SUBS_URI_VALUE / SUBS_RPC_USER / SUBS_RPC_PASSWORD.
- configurePlatform action + storeJson: rename store keys subsd*→subs* and the
  field labels/descriptions (SUBS URL / SUBS RPC User / SUBS RPC Password).
- README, instructions, release notes: SUBSD→SUBS.

Note: the image's /app/setup-spacesops-env.sh still exports SUBSD_* defaults
(partial upstream refactor) — see report; vars the package does not set (e.g.
SUBS_RPC_URL) currently have no in-image default.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -101,7 +101,7 @@ declarations do not gate startup; SpacesOps handles readiness itself.)
 | `OPERATOR_SECRET_HEX` / `OPERATOR_PUBLIC_HEX` (generated or imported) | |
 | `PLATFORM_SESSION_SECRET` (generated) | |
 | `SPACED_RPC_*` (auto-wired from Spaces) | |
-| Optional: `OPERATOR_RELAY`, `PLATFORM_MODE`, `COINGECKO_*`, `SUBSD_*` (via **Configure Platform**) | |
+| Optional: `OPERATOR_RELAY`, `PLATFORM_MODE`, `COINGECKO_*`, `SUBS_*` (via **Configure Platform**) | |
 
 ## Network Access and Interfaces
 
@@ -116,7 +116,7 @@ declarations do not gate startup; SpacesOps handles readiness itself.)
 | `show-operator-credentials` | Show Operator Credentials | Enabled | Any | — | Displays the Nostr operator keypair: npub (QR), hex public key, and the masked nsec / hex secret. |
 | `import-operator-key` | Import Operator Key | Enabled | Any | 64-char hex secret key | Replaces the operator keypair. Derives the public key automatically. **Warns** that it changes the operator identity; the service restarts to apply it. |
 | `show-admin-credentials` | Show Admin Credentials | Enabled | Any | — | Displays the **fixed** built-in admin login (`admin` / `Whatever!`) with a security warning. |
-| `configure-platform` | Configure Platform | Enabled | Any | relay, mode, CoinGecko, SUBSD (all optional) | Sets the Nostr relay, theme mode, pricing, and SUBSD backend. Saving restarts the service. |
+| `configure-platform` | Configure Platform | Enabled | Any | relay, mode, CoinGecko, SUBS (all optional) | Sets the Nostr relay, theme mode, pricing, and SUBS backend. Saving restarts the service. |
 
 ## Backups and Restore
 
@@ -147,10 +147,11 @@ volume is **not** part of this package's backup.
    StartOS reverse proxy can reach the app (it otherwise binds `127.0.0.1:3000`).
 4. **Subname-purchase and pricing are off by default.** They activate only when
    you fill in the relevant fields in **Configure Platform** (`COINGECKO_*` for
-   pricing, `SUBSD_*` for subname purchase + cert-callback flows).
-5. **SUBSD is not auto-wired to the Spaces subs daemon in v1.** The Spaces subs
-   daemon listens on 7777 with a different API/auth than the SUBSD-on-7244 this
-   app expects, so SUBSD must be configured manually if used.
+   pricing, `SUBS_*` for subname purchase + cert-callback flows).
+5. **The SUBS backend is not auto-wired to the Spaces subs daemon in v1.** The
+   Spaces service's subs daemon listens on 7777 with a different API/auth than
+   the SUBS endpoint (port 7244) SpacesOps expects, so SUBS must be configured
+   manually if used.
 
 ## What Is Unchanged from Upstream
 
@@ -192,9 +193,9 @@ startos_managed_env_vars:
 optional_env_vars:          # only set when configured via configure-platform
   - COINGECKO_API_KEY
   - COINGECKO_TOKEN_COINS
-  - SUBSD_URI_VALUE
-  - SUBSD_RPC_USER
-  - SUBSD_RPC_PASSWORD
+  - SUBS_URI_VALUE
+  - SUBS_RPC_USER
+  - SUBS_RPC_PASSWORD
 admin_credentials:
   username: admin
   password: Whatever!       # FIXED, baked into image, cannot be changed