Fix date format and add missing properties

Updated date format and added placeholders for missing properties.

Author: RAPTOR7762

core/generic_small_6V_solar_panel.fzp

@@ -4,15 +4,15 @@
  <author>RAPTOR7762</author>
  <title>Generic Small 6V Solar Panel</title>
  <label>PV</label>
- <date>Fri Oct 10 2025</date>
+ <date>2025-10-10</date>
  <tags/>
  <properties>
   <property name="family">Solar Panel</property>
-  <property name="part number"></property>
-  <property name="layer"></property>
+  <property name="part number">?</property>
+  <property name="layer">?</property>
   <property name="variant">6V Small</property>
-  <property name="mpn"></property>
-  <property name="mn"></property>
+  <property name="mpn">?</property>
+  <property name="mn">?</property>
  </properties>
  <description>Generic Solar Panel</description>
  <views>