Migrate to templ: Convert all HTML templates to type-safe templ components

- Add templ dependency for type-safe HTML rendering
- Convert index.html, login.html, register.html, dashboard.html, admin.html, admin_profile.html, admin_library.html to .templ files
- Generate Go code with templ generate for compile-time safety
- Update server routes to use templ components with proper rendering
- Refactor JavaScript in dashboard to avoid backtick parsing conflicts
- Delete old HTML template files
- Clean up project by removing unnecessary files and binaries

templates/types.go

@@ -0,0 +1,12 @@
+package templates
+
+type User struct {
+	ID       string
+	Username string
+	Email    string
+}
+
+type PageData struct {
+	User        User
+	CurrentPage string
+}