feat: v0.2.0 branding, healthz version, SSE dashboard live

Centralize APP_VERSION 0.2.0; /health and /healthz return version;
startup log line; UI title Security Alert Center v.0.2.0;
SSE /api/v1/stream/events for live dashboard counters.

backend/app/main.py

@@ -1,3 +1,4 @@
+import logging
 from contextlib import asynccontextmanager
 from pathlib import Path
 
@@ -12,8 +13,10 @@ from app.auth.api_key import hash_api_key
 from app.config import get_settings
 from app.database import SessionLocal
 from app.models import ApiKey
+from app.version import APP_VERSION, APP_VERSION_LABEL
 
 ROOT = Path(__file__).resolve().parents[2]
+logger = logging.getLogger("sac")
 
 
 def bootstrap_api_key() -> None:
@@ -42,15 +45,27 @@ def bootstrap_api_key() -> None:
 
 @asynccontextmanager
 async def lifespan(_app: FastAPI):
+    logger.info("%s — application startup (version %s)", APP_VERSION_LABEL, APP_VERSION)
     bootstrap_api_key()
     yield
+    logger.info("%s — application shutdown", APP_VERSION_LABEL)
+
+
+def configure_logging() -> None:
+    if logging.getLogger().handlers:
+        return
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(levelname)s:     %(message)s",
+    )
 
 
 def create_app() -> FastAPI:
+    configure_logging()
     settings = get_settings()
     app = FastAPI(
         title="Security Alert Center",
-        version="0.1.0",
+        version=APP_VERSION,
         lifespan=lifespan,
     )
     origins = [o.strip() for o in settings.cors_origins.split(",") if o.strip()]