Add new sections, update design system, fix header mobile layout

Sections:
- Add announcement-bar, cards, features-3col-cards, hero-card-homepage, hero-card-page, hero-slider
- Rename content-image-right → content-image (image-left layout, better mobile stacking)

Design system:
- Add cards-grid global class (flex-wrap for fluid wrapping card grids)
- Update feature-card with responsive _widthMax constraints (33%/50%/95%)
- Document Bricks Style Manager spacing setup in design.md

Headers:
- Fix header-with-cta mobile hamburger positioning — wrap nav+button in block element with row-reverse on mobile

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

sections/announcement-bar.json

@@ -0,0 +1,134 @@
+{
+  "title": "BCW — Announcement Bar",
+  "type": "section",
+  "templateType": "section",
+  "content": [
+    {
+      "id": "sec001",
+      "name": "section",
+      "parent": 0,
+      "children": ["con001"],
+      "settings": {
+        "_background": {
+          "color": {
+            "raw": "var(--color-primary-dark)"
+          }
+        },
+        "_typography": {
+          "color": {
+            "raw": "var(--color-white)"
+          },
+          "font-size": "12",
+          "font-weight": "600"
+        },
+        "_padding": {
+          "top": "10",
+          "bottom": "10"
+        }
+      },
+      "label": "Announcement Bar"
+    },
+    {
+      "id": "con001",
+      "name": "container",
+      "parent": "sec001",
+      "children": ["blk001", "blk002"],
+      "settings": {
+        "_direction": "row",
+        "_justifyContent": "space-between",
+        "_direction:mobile_portrait": "column",
+        "_alignItems:mobile_portrait": "center"
+      }
+    },
+    {
+      "id": "blk001",
+      "name": "block",
+      "parent": "con001",
+      "children": ["ico001", "txt001"],
+      "settings": {
+        "_direction": "row",
+        "_justifyContent": "flex-start",
+        "_justifyContent:mobile_portrait": "center",
+        "_width": "max-content",
+        "_alignItems": "center"
+      },
+      "label": "Left Info"
+    },
+    {
+      "id": "ico001",
+      "name": "icon",
+      "parent": "blk001",
+      "children": [],
+      "settings": {
+        "icon": {
+          "library": "themify",
+          "icon": "ti-location-pin"
+        },
+        "iconSize": "24px",
+        "_padding": {
+          "right": "10"
+        },
+        "_typography": {
+          "font-size": "22"
+        }
+      }
+    },
+    {
+      "id": "txt001",
+      "name": "text-basic",
+      "parent": "blk001",
+      "children": [],
+      "settings": {
+        "text": "123 Your Street, City, State ZIP",
+        "_typography": {
+          "font-size": "13"
+        }
+      }
+    },
+    {
+      "id": "blk002",
+      "name": "block",
+      "parent": "con001",
+      "children": ["ico002", "txt002"],
+      "settings": {
+        "_direction": "row",
+        "_justifyContent": "flex-end",
+        "_justifyContent:mobile_portrait": "center",
+        "_width": "max-content",
+        "_alignItems": "center"
+      },
+      "label": "Right Info"
+    },
+    {
+      "id": "ico002",
+      "name": "icon",
+      "parent": "blk002",
+      "children": [],
+      "settings": {
+        "icon": {
+          "library": "themify",
+          "icon": "ti-headphone"
+        },
+        "iconSize": "24px",
+        "_padding": {
+          "right": "10"
+        },
+        "_typography": {
+          "font-size": "22"
+        }
+      }
+    },
+    {
+      "id": "txt002",
+      "name": "text-basic",
+      "parent": "blk002",
+      "children": [],
+      "settings": {
+        "text": "Tel: +1 000-000-0000",
+        "_typography": {
+          "font-size": "13"
+        }
+      }
+    }
+  ]
+}