refactor(server): split hivemind monolith into modular package

- server_hivemind_5_0.py: 744-line monolith → 19-line entry point shim
- hivemind/ package (8 files, gitignored): config, sessions, xray,
  admob, management, api, main, README
- Encapsulated locks in classes (SessionStore, XrayManager,
  AdMobVerifier) — fixes 3 critical race conditions
- Added localhost-gated /api/swarm and /api/log with log ring buffer
- swarm_watch.py: Rich TUI monitor for local server dashboards
- Backed up original monolith to backups/hivemind_backup_2.py

.gitignore

@@ -86,5 +86,9 @@ xray_config_reality.json
 SERVER_DEPLOYMENT.md
 swarm_watch.py
 nginx_hivemind_reality.conf
-nginx_hivemind_reality.conf
-nginx_hivemind_reality.conf
+
+# Hivemind server package (deployed separately)
+hivemind/
+
+# Thin entry point (imports from hivemind/)
+server_hivemind_5_0.py