Rename tabs: Camera, Calibration, Trajectory — remove overlay

- Tab 1: Camera (raw feeds)
- Tab 2: Calibration (3D court + calibrate button, as before)
- Tab 3: Trajectory (disabled until calibrated)
- Remove unnecessary calibration overlay from Camera tab

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/web/app.py

@@ -30,7 +30,7 @@ state = {
 
 @app.route('/')
 @app.route('/<tab>')
-def index(tab='detection'):
+def index(tab='camera'):
     return render_template('index.html', active_tab=tab)