feat: add default canonical URL handling

- Introduce a new before_action to set the default canonical URL
- Implement set_canonical_url method to manage canonical URLs
- Update application helper to use the canonical URL for meta tags

This change enhances SEO by ensuring that the canonical URL is set
correctly for each page, preventing duplicate content issues. The
canonical URL is derived from the original request URL, excluding
query parameters.

app/controllers/application_controller.rb

@@ -3,6 +3,7 @@ class ApplicationController < ActionController::Base
   # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
   before_action :log_browser_info
   before_action :set_content_type_for_rss, if: -> { request.format.rss? }
+  before_action :set_default_canonical_url
   # allow_browser versions: :modern
   # allow_browser versions: :modern,
   #               patterns: [
@@ -74,6 +75,10 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def set_canonical_url(url = nil)
+    @canonical_url = url || request.original_url.split("?").first
+  end
+
   private
 
   def set_locale(&action)
@@ -127,4 +132,8 @@ class ApplicationController < ActionController::Base
   def set_content_type_for_rss
     response.headers["Content-Type"] = "application/rss+xml; charset=utf-8"
   end
+
+  def set_default_canonical_url
+    @canonical_url = request.original_url.split("?").first
+  end
 end

app/helpers/application_helper.rb

@@ -34,6 +34,7 @@ module ApplicationHelper
       keywords: t("meta.default.keywords", default: "AI weather art, weather visualization, city weather, artificial intelligence"),
       separator: "—".html_safe,
       reverse: true,
+      canonical: @canonical_url,
       og: {
         site_name: t("site_name", default: "TodayAIWeather"),
         type: "website",