[AZ-180] Add Jetson Orin Nano support with INT8 TensorRT engine

- Dockerfile.jetson: JetPack 6.x L4T base image (aarch64), TensorRT and PyCUDA from apt
- requirements-jetson.txt: derived from requirements.txt, no pip tensorrt/pycuda
- docker-compose.jetson.yml: runtime: nvidia for NVIDIA Container Runtime
- tensorrt_engine.pyx: convert_from_source accepts optional calib_cache_path; INT8 used when cache present, FP16 fallback; get_engine_filename encodes precision suffix to avoid engine cache confusion
- inference.pyx: init_ai tries INT8 engine then FP16 on lookup; downloads calibration cache before conversion thread; passes cache path through to convert_from_source
- constants_inf: add INT8_CALIB_CACHE_FILE constant
- Unit tests for AC-3 (INT8 flag set when cache provided) and AC-4 (FP16 when no cache)

Made-with: Cursor

_docs/04_deploy/containerization.md

@@ -115,6 +115,30 @@ networks:
 
 Already exists: `e2e/docker-compose.test.yml`. No changes needed — supports both `cpu` and `gpu` profiles with mock services and test runner.
 
+### detections-jetson (Dockerfile.jetson)
+
+| Aspect | Specification |
+|--------|--------------|
+| Base image | `nvcr.io/nvidia/l4t-base:r36.3.0` (JetPack 6.x, aarch64) |
+| TensorRT | Pre-installed via JetPack — `python3-libnvinfer` apt package (NOT pip) |
+| PyCUDA | Pre-installed via JetPack — `python3-pycuda` apt package (NOT pip) |
+| Build stages | Single stage (Cython compile requires gcc) |
+| Non-root user | `adduser --disabled-password --gecos '' appuser` + `USER appuser` |
+| Exposed ports | 8080 |
+| Entrypoint | `uvicorn main:app --host 0.0.0.0 --port 8080` |
+| Runtime | Requires NVIDIA Container Runtime (`runtime: nvidia` in docker-compose) |
+
+**Jetson-specific behaviour**:
+- `requirements-jetson.txt` derives from `requirements.txt` — `tensorrt` and `pycuda` are excluded from pip and provided by JetPack
+- Engine filename auto-encodes CC+SM (e.g. `azaion.cc_8.7_sm_16.engine` for Orin Nano), ensuring the Jetson engine is distinct from any x86-cached engine
+- INT8 is used when `azaion.int8_calib.cache` is available on the Loader service; precision suffix appended to engine filename (`*.int8.engine`); FP16 fallback when cache is absent
+- `docker-compose.jetson.yml` uses `runtime: nvidia` for the NVIDIA Container Runtime
+
+**Compose usage on Jetson**:
+```bash
+docker compose -f docker-compose.jetson.yml up
+```
+
 ## Image Tagging Strategy
 
 | Context | Tag Format | Example |