Restructure navigation: move setup items to Settings with accordion menu

Move rarely-used setup items from main sidebar to Settings to keep
daily-use features prominent:

- Services → Settings > Business section
- Locations → Settings > Business section
- Site Builder → Settings > Branding section

Settings sidebar changes:
- Convert static sections to accordion (one open at a time)
- Auto-expand section based on current URL
- Preserve all permission checks for moved items

Add redirects from old URLs to new locations for backwards compatibility.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/i18n/locales/en.json

@@ -2042,6 +2042,14 @@
       "title": "Business Hours",
       "description": "Operating hours"
     },
+    "services": {
+      "title": "Services",
+      "description": "Manage your services"
+    },
+    "locations": {
+      "title": "Locations",
+      "description": "Business locations"
+    },
     "appearance": {
       "title": "Appearance",
       "description": "Logo, colors, theme"
@@ -2082,6 +2090,10 @@
       "step2": "Copy the embed code and paste it into your website's HTML where you want the booking widget to appear.",
       "step3": "For platforms like WordPress, Squarespace, or Wix, look for an \"HTML\" or \"Embed\" block and paste the code there."
     },
+    "siteBuilder": {
+      "title": "Site Builder",
+      "description": "Build your booking site"
+    },
     "api": {
       "title": "API & Webhooks",
       "description": "API tokens, webhooks"