Simplify calibration model, add pixel preview, and improve UI

- Replace segment-based calibration with core parameters (leds_top/right/bottom/left);
  segments are now derived at runtime via lookup tables
- Fix clockwise/counterclockwise edge traversal order for all 8 start_position/layout
  combinations (e.g. bottom_left+clockwise now correctly goes up-left first)
- Add pixel layout preview overlay with color-coded edges, LED index labels,
  direction arrows, and start position marker
- Move "Add New Device" form into a modal dialog triggered by "+" button
- Add display index selector to device settings modal
- Migrate from requirements.txt to pyproject.toml for dependency management
- Update Dockerfile and docs to use `pip install .`

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/pyproject.toml

@@ -35,6 +35,8 @@ dependencies = [
     "structlog>=24.4.0",
     "python-json-logger>=3.1.0",
     "python-dateutil>=2.9.0",
+    "python-multipart>=0.0.12",
+    "wmi>=1.5.1; sys_platform == 'win32'",
 ]
 
 [project.optional-dependencies]
@@ -48,9 +50,9 @@ dev = [
 ]
 
 [project.urls]
-Homepage = "https://github.com/yourusername/wled-screen-controller"
-Repository = "https://github.com/yourusername/wled-screen-controller"
-Issues = "https://github.com/yourusername/wled-screen-controller/issues"
+Homepage = "https://git.dolgolyov-family.by/alexei.dolgolyov/wled-screen-controller-mixed"
+Repository = "https://git.dolgolyov-family.by/alexei.dolgolyov/wled-screen-controller-mixed"
+Issues = "https://git.dolgolyov-family.by/alexei.dolgolyov/wled-screen-controller-mixed/issues"
 
 [tool.setuptools]
 package-dir = {"" = "src"}