feat: add Textual TUI with auto-refresh, leaders, playoff picture, and box score

Introduces an interactive terminal UI via the `--tui` flag backed by the
Textual framework. Scores and standings auto-refresh on a configurable
interval (default 60s, minimum 10s) using asyncio with nba_api calls
offloaded to a thread pool to keep the event loop unblocked.

New tabs:
- Scores / Standings (existing views, now live-updating)
- Leaders: top-25 by stat category, cycle with < / > keys
- Playoff Picture: conference seeding with clinch/elimination status
- Box Score: per-player live stats, load any game with keys 1–9

Refactored scores.py and standings.py to separate rendering from I/O
(get_scoreboard_table, get_east/west_standings_table), keeping the
existing static CLI path fully intact. Added -sc / -st shortcut flags.

Adds textual>=0.89.1,<7.0 dependency, build-system declaration for uv,
and package-data entry for the bundled .tcss stylesheet.

1 files changed, 58 insertions, 0 deletions

diff --git a/nba/tui/styles.tcss b/nba/tui/styles.tcss
new file mode 100644
index 0000000..816608c
--- /dev/null
+++ b/nba/tui/styles.tcss
@@ -0,0 +1,58 @@
+Screen {
+    background: $background;
+}
+
+TabbedContent {
+    height: 1fr;
+}
+
+TabPane {
+    overflow: auto auto;
+    padding: 1 2;
+}
+
+/* Scores tab */
+#scores-content {
+    width: auto;
+}
+
+/* Standings & Playoff tabs — two columns side by side */
+#standings-container,
+#playoff-container,
+#boxscore-container {
+    height: 1fr;
+    width: 100%;
+}
+
+#east-content,
+#west-content,
+#playoff-east-content,
+#playoff-west-content {
+    width: 1fr;
+    overflow: auto auto;
+    padding-right: 2;
+}
+
+/* Leaders tab */
+#leaders-content {
+    width: auto;
+    overflow: auto auto;
+}
+
+/* Box Score tab */
+#home-content,
+#away-content {
+    width: 1fr;
+    overflow: auto auto;
+    padding-right: 2;
+}
+
+/* Countdown / status bar */
+#countdown {
+    dock: bottom;
+    height: 1;
+    background: $panel;
+    color: $text-muted;
+    content-align: right middle;
+    padding-right: 2;
+}