Add README.md to every directory

Each subdirectory now has a README with:
- File inventory table
- Usage guidelines and specifications
- Technical details (viewbox, colors, sizes)
- Cross-references to related assets

source/README.md

@@ -0,0 +1,17 @@
+# Source Files
+
+Master editable design files. These are the originals from the May 2023 rebrand.
+
+## Files
+
+| File                      | Format              | Description                                    |
+|---------------------------|---------------------|------------------------------------------------|
+| `keylink-it-logos.ai`     | Adobe Illustrator   | Master file with all logo variants and layers  |
+| `keylink-logo-sheet.pdf`  | PDF                 | Visual reference sheet: all marks, colors, type |
+
+## Notes
+
+- The `.ai` file is the single source of truth for all logo exports.
+- Open with Adobe Illustrator CC 2020 or later.
+- When exporting new variants, follow the naming convention in the root README.
+- The PDF logo sheet is useful as a quick handoff reference for print vendors and apparel decorators.