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

icons/favicon/README.md

@@ -0,0 +1,18 @@
+# Favicon
+
+Browser favicon for keylinkit.com and related web properties.
+
+## Files
+
+| File                   | Description                                       |
+|------------------------|---------------------------------------------------|
+| `keylink-favicon.png`  | Circular K colormark, white on cobalt blue        |
+
+## Implementation
+
+Use at 16x16, 32x32, and 180x180 (Apple touch icon). The circular crop of the K monomark ensures readability at small sizes.
+
+```html
+<link rel="icon" type="image/png" href="/favicon.png">
+<link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png">
+```