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/auth/jwt_auth.py

@@ -16,18 +16,11 @@ def create_access_token(subject: str) -> str:
     return jwt.encode(payload, settings.jwt_secret, algorithm=settings.jwt_algorithm)
 
 
-def get_current_user(
-    credentials: HTTPAuthorizationCredentials | None = Depends(bearer_scheme),
-) -> str:
-    if credentials is None or credentials.scheme.lower() != "bearer":
-        raise HTTPException(
-            status_code=status.HTTP_401_UNAUTHORIZED,
-            detail="Not authenticated",
-        )
+def _decode_username(token: str) -> str:
     settings = get_settings()
     try:
         payload = jwt.decode(
-            credentials.credentials,
+            token,
             settings.jwt_secret,
             algorithms=[settings.jwt_algorithm],
         )
@@ -37,3 +30,19 @@ def get_current_user(
         return str(username)
     except JWTError as exc:
         raise HTTPException(status_code=401, detail="Invalid token") from exc
+
+
+def verify_access_token(token: str) -> str:
+    """Проверка JWT (в т.ч. query-параметр для SSE)."""
+    return _decode_username(token)
+
+
+def get_current_user(
+    credentials: HTTPAuthorizationCredentials | None = Depends(bearer_scheme),
+) -> str:
+    if credentials is None or credentials.scheme.lower() != "bearer":
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Not authenticated",
+        )
+    return _decode_username(credentials.credentials)