feat(console): improve training data collection and best-fit persistence

- Add verbose per-file and per-sheet-size console output during collection
- Skip already-processed parts at the sheet-size level instead of all-or-nothing
- Precompute best-fits once per part and reuse across all sheet sizes
- Clear best-fit cache after each part to prevent memory growth
- Save best-fits in separate bestfits/ zip entries instead of embedding in nest.json
- Filter to Keep=true results only and scope to plate sizes in the nest
- Set nest name to match filename (includes sheet size and part count)
- Add TrainingDatabase with per-run skip logic and SQLite schema

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

collect-training-data.ps1

@@ -0,0 +1,10 @@
+param(
+    [Parameter(Mandatory, Position = 0)]
+    [string]$DxfDir
+)
+
+$DbPath = Join-Path $PSScriptRoot 'test-training.db'
+$SaveDir = 'X:\'
+$Template = 'X:\Template.nstdot'
+
+dotnet run --project (Join-Path $PSScriptRoot 'OpenNest.Console') -- --collect $DxfDir --db $DbPath --save-nests $SaveDir --template $Template