Add specs for Hatchbox PETG line and 1kg packages for current colors

[crzykidd]

Fills out the Hatchbox PETG line — adds print specifications to all existing colors,
adds the missing Red color, and adds 1kg packages for the colors currently sold.

Materials (26)

• 25 existing PETG colors enriched with the full property block; 1 new color added (Red PETG).
• Properties: density 1.27 g/cm³, nozzle 230–260 °C, bed 0–85 °C.
  • Bed min = 0 °C: Hatchbox's product listing states "No Heating Bed Required", so an
    unheated bed is manufacturer-supported. Bed max = 85 °C from real-world slicer settings
    (first layer 80 °C / other layers 85 °C); 85 is the practical PETG ceiling.
  • "Hydrophobic / doesn't absorb moisture" per Hatchbox → no drying settings.
• Colors and photos were already present (unchanged). Red PETG added with its hex + photo.
• Values with no schema field (retraction, skirt, layer-specific temps) are omitted.

Packages (8, new)

• 1kg packages on hatchbox-spool-1kg for the colors currently listed: Black, Brown, Green,
  Light Brown, Orange, Red, Silver, White.
• Per-color product URL on each package. GTIN-less for now (backfillable later).
• Colors no longer sold in this line were left specs-only (no package).

Source: https://www.hatchbox3d.com/collections/petg-1-75mm
make validate passes; README/manifest untouched.