feat: align portal center panel with side cards + redesign login page

- Portal: wrap .panel-head in matching card (border, radius, shadow) with
  cyan->purple left accent bar; h2 28px -> 20px; description right-aligned
  with vertical divider; top edge now aligns with side-menu & links-panel
- Login: switch from absolute-positioned icons to el-input prefix slot;
  layout brand row (logo + title + uppercase subtitle); add form-title
  section with gradient bar; consistent cyan focus; gradient button;
  dashed top divider for back-link; card width 420 -> 460
- Add .gitignore (node_modules, dist, __pycache__, .env, etc.)

backend/config.py

@@ -0,0 +1,17 @@
+import os
+
+BASE_DIR = os.path.dirname(os.path.abspath(__file__))
+UPLOAD_DIR = os.environ.get("OPS_UPLOAD_DIR", os.path.join(BASE_DIR, "uploads"))
+UPLOAD_URL_PREFIX = os.environ.get("OPS_UPLOAD_URL_PREFIX", "/uploads")
+
+
+class Config:
+    SECRET_KEY = os.environ.get("OPS_SECRET_KEY", "ops-portal-dev-secret-change-me-32b!")
+    SQLALCHEMY_DATABASE_URI = os.environ.get(
+        "OPS_DATABASE_URL", "sqlite:///" + os.path.join(BASE_DIR, "instance", "ops_portal.db")
+    )
+    SQLALCHEMY_TRACK_MODIFICATIONS = False
+    JWT_EXPIRE_HOURS = int(os.environ.get("OPS_JWT_EXPIRE_HOURS", "12"))
+    MAX_CONTENT_LENGTH = 32 * 1024 * 1024
+    JSON_AS_ASCII = False
+    UPLOAD_FOLDER = UPLOAD_DIR