style: darken form-field text and placeholders globally

Single CSS rule in globals.css makes typed text gray-900 and placeholders
gray-500 across all 15 field-bearing components. Element selector specificity
(0,0,1) is lower than any existing Tailwind utility so no per-component
overrides are affected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CPf5Rc8QPx6V8KLEEgfKEQ

app/globals.css

@@ -24,3 +24,14 @@ body {
   color: var(--foreground);
   font-family: Arial, Helvetica, sans-serif;
 }
+
+input,
+textarea,
+select {
+  color: #111827; /* gray-900 — dark typed text */
+}
+
+input::placeholder,
+textarea::placeholder {
+  color: #6b7280; /* gray-500 — readable placeholder */
+}