release(v1.7.2-alpha): fix Install Update + identity avatar backfill + label

Three user-visible fixes shipped together.

1. update.apply permission-denied
   apply_update() was doing fs::copy into /usr/local/bin/archipelago and
   tar xzf into /opt/archipelago as the archipelago user — both root-owned.
   The backup step succeeded (it wrote to data_dir) but the swap failed
   with a silent permission denied, wrapped as "Failed to apply archipelago".
   Now uses `sudo install -m 0755` for the binary and `sudo tar -xzf` for
   the frontend, plus a post-apply `sudo systemctl --no-block restart
   archipelago` scheduled 2s after the RPC reply so the UI sees success.

2. Apply → Install label
   en/es locale strings: applyUpdate / applyTitle / applyNow changed from
   "Apply" to "Install". Matches the user's mental model and distinguishes
   the user-facing verb from the internal apply_update() function.

3. Identity avatar backfill
   Identities created before df83163f had profile=None on disk and so
   rendered as initials. load_record() now synthesizes an IdentityProfile
   with a default picture (identicon for regular identities, the hex node
   SVG for derivation_index=0) when profile is missing. The synthetic
   profile lives only in the returned record; the file stays untouched so
   a later explicit Save persists whatever the user actually chose.

Artefacts:
  archipelago                                        70e5444e…67c589  40381960
  archipelago-frontend-1.7.2-alpha.tar.gz            806b027b…358a824 76983699

Changelog rewritten layman-style per saved feedback.

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

neode-ui/src/locales/en.json

@@ -663,18 +663,18 @@
     "autoApply": "Auto-Apply",
     "autoApplyDesc": "Check daily and automatically install updates at 3 AM. Service restarts as needed.",
     "downloadUpdate": "Download Update",
-    "applyUpdate": "Apply Update",
+    "applyUpdate": "Install Update",
     "checkForUpdates": "Check for Updates",
     "checking": "Checking...",
     "rollback": "Rollback to Previous",
     "backToSettings": "Back to Settings",
     "percentComplete": "{percent}% complete",
     "applyWarning": "Installing components and restarting services. Do not power off.",
-    "applyTitle": "Apply Update?",
+    "applyTitle": "Install Update?",
     "applyMessage": "The backend service will restart. This may take a moment.",
     "rollbackTitle": "Rollback Version?",
     "rollbackMessage": "This will restore the previous version. The backend service will restart.",
-    "applyNow": "Apply Now",
+    "applyNow": "Install Now",
     "rollbackButton": "Rollback",
     "upToDateMessage": "Your system is up to date. No updates available. Your system is running the latest version.",
     "checkFailed": "Failed to check for updates. Check your internet connection.",