feat: add project icon picker component and integrate with project management

- Implemented ProjectIconPicker component for selecting project icons.
- Created ProjectIcon component to display selected icons.
- Updated calendar page to remove unused PageHeading component.
- Modified growth page to enhance UI and improve text clarity.
- Refactored index page to include project icons and improve layout.
- Added mine page for user profile management with avatar selection.
- Introduced projects-sort page for managing project order with drag-and-drop functionality.
- Enhanced projects page to allow icon selection when adding or editing projects.
- Updated record page to streamline user experience and improve form actions.
- Adjusted practice service to support project icon management.
- Added tests for project saving functionality to ensure correct handling of icons.
- Updated global type definitions to support SVG and PNG imports.

backend/internal/practice/icons.go

@@ -0,0 +1,12 @@
+package practice
+
+// Icon IDs address bundled artwork, never client-provided URLs or file paths.
+func validProjectIcon(id string) bool {
+	switch id {
+	case "", "plie", "tendu", "releve", "port-de-bras", "arabesque", "attitude",
+		"pirouette", "grand-jete", "foot-hip", "flexibility", "ball-core",
+		"swan-arms", "breathing", "core-glutes", "soft-shoes", "pointe-shoes", "barre", "piano":
+		return true
+	}
+	return false
+}