feat(color): add hex code display and click-to-copy functionality

Enhances SpoolIcon component with optional showHex prop:
- Displays hex color code next to swatch when enabled
- Click to copy hex code to clipboard
- Shows tooltip with copy hint
- Supports both single and multi-color filaments

Enabled on detail pages:
- Filament show page
- Spool show page

Added translation keys for copy feedback messages.

Closes #33

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/public/locales/en/common.json

@@ -52,6 +52,11 @@
         "validationError": "Validation error: {{error}}"
     },
     "kofi": "Tip me on Ko-fi",
+    "color": {
+        "click_to_copy": "Click to copy",
+        "copied": "Copied {{color}} to clipboard",
+        "copy_failed": "Failed to copy to clipboard"
+    },
     "loading": "Loading",
     "version": "Version",
     "unknown": "Unknown",