feat: initial AC telemetry Lua plugin

- CSP Lua app that reads telemetry via ac.* API
- Sends JSON over UDP to configurable target (default 127.0.0.1:5005)
- Purpose-built serializer with zero GC pressure at 60Hz
- Pre-allocated buffer tables, no per-frame allocations
- Graceful fallback when ac global is absent (testing outside AC)
- .gitignore for .idea/

main.lua

@@ -0,0 +1,8 @@
+-- main.lua - Entry point for ACTelemetry CSP Lua app
+-- CSP calls script.update(dt) every frame; we delegate to the telemetry module.
+
+local telemetry = require("src.telemetry")
+
+function script.update(dt)
+    telemetry.update(dt)
+end