Add design system, audit sections, apply global classes

Design system (design/):
- bcw-css-variables.json: color, spacing (--space-xs→2xl), typography (--h1→h6, --text-sm→xl)
- bcw-color-palette.json: named swatches referencing CSS variables
- bcw-global-classes.json: section-container, section-header, col-3, col-4, features-container, footer-sub-section
- design.md: full variable reference and usage guide

Templates:
- features-3col + features-4col: add global_classes embed + _cssGlobalClasses references
- All headers + footers: apply var(--color-primary) background to section elements
- footer-columns: add footer-sub-section class to column containers
- Remove content-image-left (duplicate of content-image-right with children reversed)
- testimonials: gap tweak 12px → 15px on card containers

Repo hygiene:
- Add .gitignore (Updated_Sections/)
- Clear Updated_Sections staging folder

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

sections/features-3col.json

@@ -2,6 +2,20 @@
   "title": "BCW — Features 3 Column",
   "type": "section",
   "templateType": "section",
+  "global_classes": [
+    {
+      "id": "features-container",
+      "name": "features-container",
+      "settings": {
+        "_typography": {
+          "text-align": "center"
+        },
+        "_rowGap": "10px"
+      },
+      "modified": 1772146285,
+      "user_id": 2
+    }
+  ],
   "content": [
     {
       "id": "sec001",
@@ -58,8 +72,8 @@
         "_direction": "row",
         "_alignItems": "flex-start",
         "_justifyContent": "center",
-
-        "_gap": "32px"
+        "_gap": "32px",
+        "_rowGap:mobile_portrait": "15px"
       },
       "label": "Features Row"
     },
@@ -71,7 +85,8 @@
       "settings": {
         "_direction": "column",
         "_alignItems": "center",
-        "_gap": "12px"
+        "_gap": "15px",
+        "_cssGlobalClasses": ["features-container"]
       },
       "label": "Feature One"
     },
@@ -109,7 +124,8 @@
       "settings": {
         "_direction": "column",
         "_alignItems": "center",
-        "_gap": "12px"
+        "_gap": "15px",
+        "_cssGlobalClasses": ["features-container"]
       },
       "label": "Feature Two"
     },
@@ -147,7 +163,8 @@
       "settings": {
         "_direction": "column",
         "_alignItems": "center",
-        "_gap": "12px"
+        "_gap": "15px",
+        "_cssGlobalClasses": ["features-container"]
       },
       "label": "Feature Three"
     },