chore: bump form input font-size to 16px to prevent iOS focus-zoom

Final retrofit in the cross-project iOS focus-zoom chore (after authd PR
#11, buchinese PR #5, inventory PR #18, movement PR #15). Enforces the
standing rule in ~/.claude/CLAUDE.md: text-entry inputs must compute to
font-size >= 16px so iOS Safari does not auto-zoom on focus.

tests/integration/style.test.ts

@@ -25,6 +25,12 @@ describe('public/style.css (file contents)', () => {
     expect(css).toContain('--font-mono');
     expect(css).toMatch(/\.share-box input\[readonly\][\s\S]*?font-family:\s*var\(--font-mono\)/);
   });
+
+  it('uses font-size >= 16px on text-entry inputs to prevent iOS focus-zoom', () => {
+    expect(css).toMatch(
+      /input\[type="text"\][\s\S]*?input\[type="password"\][\s\S]*?\{[\s\S]*?font-size:\s*(1[6-9]|[2-9]\d)px/
+    );
+  });
 });
 
 describe('GET /public/style.css', () => {