Microscope camera kiosk

Touchscreen kiosk for the Raspberry Pi HQ camera (IMX477) used as a
microscope: live preview from boot, raw frame recording, full-resolution
stills, and automatic capture-SSD mounting.

- app.py: GTK3 fullscreen UI over cage — preview, REC/STOP, PHOTO,
  90-degree rotate button, tap-to-open exposure/gain/settings sliders,
  and an "SSD NOT MOUNTED" badge
- camera.py: picamera2 wrapper with separate video (ISP preview + packed
  12-bit raw) and still (4056x3040) configurations
- recorder.py: writer thread turning the raw stream into one Bayer frame
  per file plus index.jsonl/session.json, with dropped/missed accounting
- photos.py: still capture to DNG + JPEG, and a background worker that
  renders a viewable 16-bit sRGB TIFF from the 12-bit Bayer frame
- storage.py: SSD mount state and the date/time/format session layout
- tools/unpack_raw.py: desktop-side unpacker/demosaicer
- system/ + install.sh: systemd units, udev rule, mount helper, sudoers

Note: raw frames are written byte-for-byte as the sensor produced them, so
they stay decodeable regardless of how the stills pipeline evolves.

config.json

@@ -0,0 +1,47 @@
+{
+  "archive_min_free_mb": 500,
+  "device_label": "MICROSCOPE",
+  "fs_uuid": "caf4320b-0fa3-4674-bfa9-f17f6165f681",
+  "mount_point": "/mnt/microscope",
+  "photo": {
+    "black_level": 256,
+    "buffer_count": 2,
+    "height": 3040,
+    "jpeg_quality": 95,
+    "settle_frames": 3,
+    "tiff_apply_colour_matrix": true,
+    "tiff_apply_gamma": true,
+    "tiff_apply_white_balance": true,
+    "white_level": 4095,
+    "width": 4056,
+    "write_dng": true,
+    "write_jpeg": true,
+    "write_tiff": true
+  },
+  "preview": {
+    "format": "XRGB8888",
+    "height": 600,
+    "width": 1024
+  },
+  "record": {
+    "buffer_count": 12,
+    "index_stride": 1,
+    "limit_frame_duration": true,
+    "target_fps": 30,
+    "write_queue": 8
+  },
+  "sensor": {
+    "bit_depth": 12,
+    "height": 1520,
+    "sensor_fps": 40,
+    "width": 2028
+  },
+  "ui": {
+    "fullscreen": true,
+    "hide_cursor": true,
+    "preview_refresh_ms": 33,
+    "rotation": 0,
+    "status_refresh_ms": 250,
+    "storage_poll_ms": 1000
+  }
+}