feat: architecture review fixes, self-update system, CI pipeline, supply chain hardening

Architecture review (all P0+P1 issues now fixed):
- Add 10s timeout to 6 bare Nostr client.connect() calls
- Pin all 12 crypto deps to exact versions from Cargo.lock
- Pin all 15 floating container image tags to exact patch versions
- Add CI pipeline (cargo fmt + clippy + tests, frontend type-check + build)

Self-update system (git.tx1138.com):
- scripts/self-update.sh: pull, build, install, restart with rollback
- systemd timer checks daily at 3 AM
- update.check RPC does git-based checks when repo is present
- update.git-apply RPC triggers self-update from UI
- Default update URL changed from GitHub to git.tx1138.com
- Git added to ISO package list for fresh installs

Documentation:
- CHANGELOG v1.3.1 with all changes
- README updated (version, update system section)
- BETA-PROGRESS session #6 logged
- architecture-review.html: 4 issues marked FIXED, 8/12 refactoring done

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

image-recipe/configs/archipelago-update.timer

@@ -0,0 +1,14 @@
+[Unit]
+Description=Check for Archipelago updates daily
+ConditionPathExists=/home/archipelago/archy/.git
+
+[Timer]
+# Check at 3 AM daily (low-activity window)
+OnCalendar=*-*-* 03:00:00
+# Randomize within 30 min window to avoid thundering herd
+RandomizedDelaySec=1800
+# Run once on boot if last check was missed
+Persistent=true
+
+[Install]
+WantedBy=timers.target