feat(config): let the operator turn off the breach and update checks

Two requests left the server without anything being connected: the
HaveIBeenPwned range query on every password set (registration, change,
admin reset) and the daily GitHub releases request behind the About page
and the admin version tile. Neither could be turned off, which made
"nothing leaves" untrue for an instance that wanted it to be.

PASSWORD_BREACH_CHECK_DISABLED and UPDATE_CHECK_DISABLED (1, true, yes or
on) stop each request. Both stay on by default. The breach check keeps
its fail-open contract: switched off, a password is simply not looked up.
The update route answers status "unknown" with reason "disabled" and
the admin tile says the check is off. The password routes reach the
check only through the switch, and a test holds that import line.

Both are on the compose whitelist, in the env manifest under a new
"Outbound requests" group with IP_GEO_LOOKUP_DISABLED, and documented in
both env examples and the getting-started guide.

src/components/admin/version-tile-section.tsx

@@ -80,6 +80,9 @@ export function VersionTileSection() {
 
   const newer = update?.status === "newer_available";
   const upToDate = update?.status === "up_to_date";
+  // The operator turned the GitHub request off (UPDATE_CHECK_DISABLED); say
+  // so rather than leaving the slot empty like an unreachable feed.
+  const checkOff = update?.status === "unknown" && update.reason === "disabled";
   const sha = shortSha(version?.buildSha ?? null);
 
   return (
@@ -110,6 +113,10 @@ export function VersionTileSection() {
               <CheckCircle2 className="h-3.5 w-3.5" aria-hidden="true" />
               {t("admin.overview.versionTileUpToDate")}
             </span>
+          ) : checkOff ? (
+            <span className="text-muted-foreground text-xs">
+              {t("admin.overview.versionTileCheckOff")}
+            </span>
           ) : null
         }
       />