feat(notifications): add Gotify + Apprise + Ntfy with Traefik labels and healthchecks

[achievefibromyalgia-lgtm]

Notifications Stack Implementation

Changes

• Gotify (port 8080): Self-hosted notification server with REST API and web UI
• Ntfy (port 80): Push notification service with bearer token auth support
• Apprise (port 8000): Notification aggregator supporting 50+ services

Security & Quality Fixes

1. HTTP 200 status verification in all healthchecks
2. DOMAIN variable required validation in Traefik labels
3. NTFY auth conflict resolved (removed conflicting NTFY_AUTH_FILE_REFRESH)
4. Security token generation hints in .env.example

Bounty: Issue #13 USDT

ERC20 Address: 0xaae0101ac77a2e4e0ea826eb4d309374f029b0a6

[achievefibromyalgia-lgtm]

PR #386 — Quality Improvements over #383

This PR improves upon #383 with critical fixes:

Fixed Issues:

1. Healthcheck HTTP 200 verification — All services now verify actual HTTP 200, not just endpoint existence
2. DOMAIN validation — Traefik labels now fail-fast if DOMAIN is unset (prevents silent routing failures)
3. NTFY auth conflict resolved — Removed conflicting NTFY_AUTH_FILE_REFRESH variable
4. Security token documentation — Added generation hints to .env.example

Files changed: stacks/notifications/docker-compose.yml, stacks/notifications/.env.example

Ready for review. USDT bounty claim for Issue #13.

[achievefibromyalgia-lgtm]

@illbnm Ready for review. This PR improves upon #383 with critical fixes: HTTP 200 healthcheck verification, DOMAIN validation, NTFY auth conflict resolution. All tests pass. Issue #13 USDT.

[achievefibromyalgia-lgtm]

Hi @illbnm — this PR supersedes #383 with critical fixes (HTTP 200 healthcheck, DOMAIN validation, NTFY auth conflict resolution). All tests passing. Could you take a look? Thanks!