fix: UI/UX consistency overhaul — fix 8 bugs, standardize design system

Bug fixes:
- Backup refresh no longer re-renders entire page (separate refreshing state)
- SSL cert button no longer flickers when no certs available
- Volume mode selector rewritten to use proper scope system (7 scopes)
- Navigation flicker eliminated when returning from env/volumes pages
- Logout button moved to sidebar footer near theme/locale controls
- Subdomain pattern now shows variable hint tooltip ({project}, {stage}, etc.)
- SSL certificate selector moved to Credentials page with auto-save
- Projects page now has search/filter by name, image, or registry

Consistency improvements:
- New Breadcrumb component replaces 5 inline implementations
- New IconArrowLeft, IconChevronDown components replace inline SVGs
- All inline spinners replaced with IconLoader component
- 10 semantic badge classes with dark mode variants in tokens.css
- Global disabled button cursor-not-allowed rule
- Raw inputs in auth page replaced with FormField components
- Missing aria-labels added to icon-only buttons
- Error panels standardized to use design tokens

web/src/lib/i18n/en.json

@@ -58,7 +58,9 @@
     "imageLoadFailed": "Failed to load images",
     "alreadyAdded": "Already added",
     "portHelpText": "Auto-detected from EXPOSE if empty",
-    "healthcheckHelpText": "Auto-detected from image if empty"
+    "healthcheckHelpText": "Auto-detected from image if empty",
+    "searchPlaceholder": "Search projects by name, image, or registry...",
+    "noMatchingProjects": "No projects match your search."
   },
   "projectDetail": {
     "deleteProject": "Delete Project",
@@ -162,6 +164,7 @@
     "save": "Save",
     "add": "Add",
     "adding": "Adding...",
+    "scopeGuide": "Volume Scopes",
     "noVolumes": "No volumes configured yet. Add one above.",
     "volumeAdded": "Volume added",
     "volumeUpdated": "Volume updated",
@@ -258,6 +261,11 @@
     "dockerNetworkHelp": "Docker network for deployed containers",
     "subdomainPattern": "Subdomain Pattern",
     "subdomainPatternHelp": "Pattern for auto-generated subdomains",
+    "subdomainVarsTitle": "Available variables",
+    "varProject": "Project name",
+    "varStage": "Stage name",
+    "varTag": "Image tag",
+    "varPort": "Container port",
     "pollingInterval": "Polling Interval (seconds)",
     "pollingIntervalHelp": "How often to check registries for new tags (10-86400)",
     "notificationUrl": "Notification URL",