Add cache-busting ?v= to template CSS/JS, bump version

All static asset references now include ?v={{ version }} to force
browser to reload on deploy instead of serving cached versions.
Increment TEMPLATE_VERSION in server.py on each deploy.

src/web/server.py

@@ -49,6 +49,10 @@ from ..midi.handler import MIDIHandler
 
 logger = logging.getLogger(__name__)
 
+# ── Cache buster version (bumped on deploy) ─────────────────────────
+# Increment this when template/static changes need to bypass browser cache
+TEMPLATE_VERSION = "7"
+
 # ── Defaults ─────────────────────────────────────────────────────────────────
 
 DEFAULT_HOST = "0.0.0.0"
@@ -312,6 +316,8 @@ class WebServer:
     def _build_app(self) -> FastAPI:
 
         templates = Jinja2Templates(directory=str(TEMPLATES_DIR))
+        # Inject version into all templates (cache buster for CSS/JS)
+        templates.env.globals["version"] = TEMPLATE_VERSION
 
         @asynccontextmanager
         async def lifespan(app: FastAPI):