Switch project to uv and add sticky-header scroll to dashboard table

Adds pyproject.toml, uv.lock, .python-version, and a .gitignore for uv
package management. Constrains the dashboard table to the viewport
height with a sticky thead so column headers remain visible while
scrolling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

styles.css

@@ -110,8 +110,15 @@ footer {
 /* ── Data table ─────────────────────────────────────────── */
 .table-scroll {
     overflow-x: auto;
+    overflow-y: auto;
+    max-height: calc(100vh - 340px);
     border-radius: 10px;
 }
+.table-scroll .data-table thead th {
+    position: sticky;
+    top: 0;
+    z-index: 1;
+}
 .data-table {
     width: 100%;
     border-collapse: collapse;