legal: add LICENSE, ATTRIBUTION.md, and CSS snippet headers

- Add MIT LICENSE file (was declared but missing)
- Add ATTRIBUTION.md crediting Karpathy, Nate Herk, SlRvb, and bundled plugins
- Add GPL-2.0 attribution headers to ITS-Dataview-Cards.css and ITS-Image-Adjustments.css

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

.obsidian/snippets/ITS-Dataview-Cards.css

@@ -1,3 +1,8 @@
+/* ITS Dataview Cards — by SlRvb
+ * Source: https://github.com/SlRvb/Obsidian--ITS-Theme
+ * License: GPL-2.0 (https://github.com/SlRvb/Obsidian--ITS-Theme/blob/main/LICENSE)
+ */
+
 .dvl-c .table-view-table > thead::before {
   content: "⚙";
   font-family: var(--its, var(--default-font));