Fix outdated timezone references

Updates outdated timezone identifiers in the database to their current
equivalents. This resolves ArgumentError exceptions when users have
outdated timezones like "Europe/Kiev" stored in their preferences.

Timezone mappings:
- Europe/Kiev → Europe/Kyiv
- Asia/Calcutta → Asia/Kolkata
- Asia/Katmandu → Asia/Kathmandu
- Asia/Rangoon → Asia/Yangon
- Asia/Saigon → Asia/Ho_Chi_Minh
- Pacific/Ponape → Pacific/Pohnpei
- Pacific/Truk → Pacific/Chuuk

🤖 Generated with Claude Code

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

db/migrate/20250623162207_update_outdated_timezones.rb

@@ -0,0 +1,31 @@
+class UpdateOutdatedTimezones < ActiveRecord::Migration[7.2]
+  TIMEZONE_MAPPINGS = {
+    "Europe/Kiev" => "Europe/Kyiv",
+    "Asia/Calcutta" => "Asia/Kolkata",
+    "Asia/Katmandu" => "Asia/Kathmandu",
+    "Asia/Rangoon" => "Asia/Yangon",
+    "Asia/Saigon" => "Asia/Ho_Chi_Minh",
+    "Pacific/Ponape" => "Pacific/Pohnpei",
+    "Pacific/Truk" => "Pacific/Chuuk"
+  }.freeze
+
+  def up
+    TIMEZONE_MAPPINGS.each do |old_tz, new_tz|
+      execute <<-SQL
+        UPDATE families 
+        SET timezone = '#{new_tz}' 
+        WHERE timezone = '#{old_tz}'
+      SQL
+    end
+  end
+
+  def down
+    TIMEZONE_MAPPINGS.each do |old_tz, new_tz|
+      execute <<-SQL
+        UPDATE families 
+        SET timezone = '#{old_tz}' 
+        WHERE timezone = '#{new_tz}'
+      SQL
+    end
+  end
+end