Bump zot registry to v2.1.15 (#293)

## Summary
- Upgrade zot OCI registry from v2.1.13 to v2.1.15 on indri
- Addresses CVE-2025-30204 (golang-jwt memory) and open redirect via callback_ui
- No config template changes needed (externalUrl is auto-allowlisted)
- Requires Go 1.25.7 (bump from 1.25.6 via mise)

## Data Safety
- Data directory ~/erichblume/zot is NOT touched during build or deploy
- No schema migrations in v2.1.14 or v2.1.15
- Storage format remains OCI spec 1.1.0

## Deployment Steps
- [ ] SSH to indri: bump Go to 1.25.7 via `mise use go@1.25.7`
- [ ] Fetch and checkout v2.1.15 in ~/code/3rd/zot
- [ ] Build: `mise x -- make binary`
- [ ] Restart LaunchAgent
- [ ] Verify: `curl -s http://localhost:5050/v2/` returns 200
- [ ] Verify: `curl -s https://registry.ops.eblu.me/v2/_catalog` lists repos
- [ ] Verify: `mise run services-check`

Reviewed-on: #293

service-versions.yaml

@@ -269,8 +269,8 @@ services:
 
   - name: zot
     type: ansible
-    last-reviewed: null
-    current-version: null
+    last-reviewed: 2026-03-14
+    current-version: "v2.1.15"
     upstream-source: https://github.com/project-zot/zot/releases
     notes: Built from source on indri