Add SnapForm panels, preferences, properties, and runtime management

- Implemented RuntimeModelsPanel and DebugPanel for UI integration in Blender.
- Created SnapFormPreferences to manage user settings for storage and runtime configuration.
- Defined SnapFormSettings to hold various properties related to input, model selection, and export options.
- Developed runtime management functions for installation, model downloading, and reconstruction commands.
- Added status bar functionality to display job progress and status in the Blender UI.
- Implemented worker script for handling model downloads and depth reconstruction tasks.
- Introduced unit tests for download progress reporting and image depth extraction functionalities.

src/snapform/preferences.py

@@ -0,0 +1,52 @@
+import shutil
+from pathlib import Path
+
+import bpy
+
+
+class SnapFormPreferences(bpy.types.AddonPreferences):
+    bl_idname = __package__
+
+    storage_root: bpy.props.StringProperty(
+        name="Storage Root",
+        description=(
+            "Shared user-writable storage for Runtime, models and jobs; "
+            "all Blender versions can use the same directory"
+        ),
+        subtype="DIR_PATH",
+        default=str(Path.home() / ".snapform"),
+    )
+    uv_executable: bpy.props.StringProperty(
+        name="uv Executable",
+        description="Path to uv; a command name is accepted when uv is on PATH",
+        subtype="FILE_PATH",
+        default=shutil.which("uv") or "uv",
+    )
+    torch_backend: bpy.props.EnumProperty(
+        name="Torch Backend",
+        description="PyTorch build installed into the isolated Runtime",
+        items=(
+            ("CU128", "CUDA 12.8", "NVIDIA CUDA 12.8 PyTorch wheels"),
+            ("CPU", "CPU", "CPU-only PyTorch wheels"),
+        ),
+        default="CU128",
+    )
+
+    def draw(self, _context):
+        from .runtime import runtime_directory, runtime_ready
+
+        layout = self.layout
+        layout.prop(self, "storage_root")
+        layout.prop(self, "uv_executable")
+        layout.prop(self, "torch_backend")
+        layout.separator()
+        layout.label(text=f"Runtime: {runtime_directory()}")
+        if runtime_ready():
+            layout.label(text="Runtime is ready", icon="CHECKMARK")
+        else:
+            operator = layout.operator(
+                "snapform.run_job",
+                text="Install Runtime",
+                icon="IMPORT",
+            )
+            operator.job_type = "INSTALL_RUNTIME"