Add HL3D branding, Etsy Live/Draft paging and Projects lifecycle

Replace the old touchmark/PNG identity with the supplied lockup and
monogram, segmented role-aware navigation, Live/Draft listing filters
with generation-based cache invalidation, and admin Projects covering
immutable file revisions, listing live pointers, and exact-decimal
filament/packaging/shipping costing. Additive schema only; no Etsy
publication. Isolated clone tests: 301 tests, 1162 assertions.

app/Models/ProjectFile.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace App\Models;
+
+use Database\Factories\ProjectFileFactory;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class ProjectFile extends Model
+{
+    /** @use HasFactory<ProjectFileFactory> */
+    use HasFactory;
+
+    /** @var list<string> */
+    public const EXTENSIONS = ['stl', '3mf', 'gcode'];
+
+    protected $fillable = [
+        'revision_id', 'role', 'original_filename', 'storage_key', 'extension',
+        'media_type', 'byte_size', 'sha256', 'uploaded_by', 'printer_profile', 'material',
+    ];
+
+    public function revision(): BelongsTo
+    {
+        return $this->belongsTo(ProjectRevision::class, 'revision_id');
+    }
+
+    public function uploader(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'uploaded_by');
+    }
+}