fix: use fixed width for payee column in Activity panel

Ensures account names are consistently left-aligned by using a fixed
220px width for the payee column instead of flexible 1fr.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: robcohen

src/style.css

@@ -1373,7 +1373,7 @@ a:focus-visible {
 
 .tx-row {
     display: grid;
-    grid-template-columns: 85px minmax(0, 1fr) minmax(0, 1fr) auto;
+    grid-template-columns: 85px 220px 1fr auto;
     gap: 8px;
     padding: 5px 16px;
     font-size: 12px;