Add NexusAI: universal MCP service (TTS/STT/image/video/music/web-search)

Monorepo-lite with shared @nexusai/core and @nexusai/mcp-server (stdio).
Provider-agnostic tools with explicit provider selection; NordRouter adapter
(media generate/poll/download, estimate, upload, models) and search via
perplexity/sonar. Local STT via faster-whisper uv sidecar. SQLite journal of
every generation for usage stats and future admin. 10 MCP tools.

NexusAI/.gitignore

@@ -0,0 +1,25 @@
+
+# secrets
+api-sec.txt
+.env
+.env.*
+!.env.example
+
+# node
+node_modules/
+**/dist/
+*.tsbuildinfo
+
+# data / media
+media-output/
+*.sqlite
+*.sqlite-journal
+*.db
+
+# python
+sidecar/.venv/
+__pycache__/
+*.pyc
+
+# os
+.DS_Store