feat: modular synth, sandbox, code editor, pixel editor, Docker deployment

Synth:
- Modular synth with Tone.js: oscillator, LFO, noise, filter, envelope, VCA, mixer, delay, reverb, distortion, output
- Keyboard widget (mini SVG + fullscreen piano + computer keys Z-M/Q-I)
- Drum pad (4x4 grid, 16 pads with MIDI notes, matching reaktor)
- Sequencer (SVG bar grid with pitch/gate editing, matching reaktor)
- Live modulation visualization (LFO waveform simulation, envelope, noise)
- Knob with drag, wheel, double-click inline edit, modulation glow ring
- Pan/zoom viewport, bezier wires colored by port type
- Play/Stop audio lifecycle, stereo output with Tone.Merge

Sandbox:
- New /sandbox page with all editors in freeform mode
- Synth fills full viewport height

Workbenches:
- Code Editor (Monaco) with test cases
- Signal Playground (Web Audio oscillator + filter + visualizer)
- Pixel Editor (grid canvas with palette and match mode)

Deployment:
- Dockerfile (multi-stage Next.js standalone build)
- .dockerignore
- next.config.ts output: standalone
- Gitea remote configured

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

package.json

@@ -11,6 +11,7 @@
   "dependencies": {
     "@base-ui/react": "^1.3.0",
     "@dagrejs/dagre": "^3.0.0",
+    "@monaco-editor/react": "^4.7.0",
     "@types/katex": "^0.16.8",
     "@xyflow/react": "^12.10.1",
     "class-variance-authority": "^0.7.1",
@@ -22,6 +23,7 @@
     "react-dom": "19.2.4",
     "shadcn": "^4.1.0",
     "tailwind-merge": "^3.5.0",
+    "tone": "^15.1.22",
     "tw-animate-css": "^1.4.0",
     "zustand": "^5.0.12"
   },