perf(savings_goals/show): preload + memoize cut show from 17 to 5 queries

- set_savings_goal: with_current_balance + includes(savings_contributions: :account, linked_accounts: []) so contributions / accounts / current balance don't re-query inside helpers and view partials
- SavingsGoal#status + #average_monthly_contribution: defined?(@ivar) memoization so the 5+ callsites per show (header banner, projection_summary, donut, goal-card pace, stats_for) don't recompute the exists?/MIN/SUM triplet each time
- SavingsGoal#projection_payload: sort loaded contributions in Ruby instead of running a fresh ORDER BY
- SavingsGoalsController#show: replace .chronological re-query with in-memory sort over the preloaded association
- funding_breakdown_for: group_by + transform_values off the loaded collection instead of an extra GROUP BY SQL
- stats_for: contributions_count uses .size to read the loaded cache instead of issuing COUNT(*)

app/controllers/savings_goals_controller.rb

@@ -24,7 +24,9 @@ class SavingsGoalsController < ApplicationController
   end
 
   def show
-    @contributions = @savings_goal.savings_contributions.includes(:account).chronological
+    @contributions = @savings_goal.savings_contributions
+                                  .sort_by { |c| [ c.contributed_at, c.created_at ] }
+                                  .reverse
     @funding_breakdown = funding_breakdown_for(@savings_goal)
     @stats = stats_for(@savings_goal)
     @breadcrumbs = [
@@ -114,7 +116,10 @@ class SavingsGoalsController < ApplicationController
 
   private
     def set_savings_goal
-      @savings_goal = Current.family.savings_goals.find(params[:id])
+      @savings_goal = Current.family.savings_goals
+                             .with_current_balance
+                             .includes(savings_contributions: :account, linked_accounts: [])
+                             .find(params[:id])
     end
 
     def savings_goal_params
@@ -156,8 +161,8 @@ class SavingsGoalsController < ApplicationController
 
     def funding_breakdown_for(goal)
       totals = goal.savings_contributions
-                   .group(:account_id)
-                   .sum(:amount)
+                   .group_by(&:account_id)
+                   .transform_values { |arr| arr.sum(&:amount) }
       goal.linked_accounts.map do |account|
         amount = totals[account.id] || 0
         { account: account, amount: amount, money: Money.new(amount, goal.currency) }
@@ -219,7 +224,7 @@ class SavingsGoalsController < ApplicationController
       {
         avg_monthly: avg,
         avg_monthly_sub: sub_avg,
-        contributions_count: goal.savings_contributions.count,
+        contributions_count: goal.savings_contributions.size,
         monthly_target_sub: sub_target,
         projection_summary: summary
       }

app/models/savings_goal.rb

@@ -139,7 +139,7 @@ class SavingsGoal < ApplicationRecord
   # date ascending. Consumed by the
   # `savings-goal-projection-chart` Stimulus controller.
   def projection_payload
-    sorted = savings_contributions.order(contributed_at: :asc).to_a
+    sorted = savings_contributions.sort_by(&:contributed_at)
     running = 0
     saved_series = sorted.map do |c|
       running += c.amount.to_d
@@ -167,26 +167,38 @@ class SavingsGoal < ApplicationRecord
   # :behind → has target_date and current pace < required monthly pace
   # :no_target_date → progress < 100 and target_date is nil
   def status
-    return :reached if progress_percent >= 100
-    return :no_target_date if target_date.nil?
-    return :on_track if monthly_target_amount.to_d <= average_monthly_contribution.to_d
+    return @status if defined?(@status)
 
-    :behind
+    @status = if progress_percent >= 100
+      :reached
+    elsif target_date.nil?
+      :no_target_date
+    elsif monthly_target_amount.to_d <= average_monthly_contribution.to_d
+      :on_track
+    else
+      :behind
+    end
   end
 
   def average_monthly_contribution
-    return 0 if savings_contributions.empty?
+    return @average_monthly_contribution if defined?(@average_monthly_contribution)
 
-    first_at = if savings_contributions.loaded?
-      savings_contributions.map(&:contributed_at).compact.min
+    @average_monthly_contribution = if savings_contributions.empty?
+      0
     else
-      savings_contributions.minimum(:contributed_at)
+      first_at = if savings_contributions.loaded?
+        savings_contributions.map(&:contributed_at).compact.min
+      else
+        savings_contributions.minimum(:contributed_at)
+      end
+      if first_at.blank?
+        current_balance
+      else
+        months = ((Date.current.year - first_at.year) * 12 + (Date.current.month - first_at.month)) + 1
+        months = 1 if months < 1
+        (current_balance.to_d / months).round(2)
+      end
     end
-    return current_balance if first_at.blank?
-
-    months = ((Date.current.year - first_at.year) * 12 + (Date.current.month - first_at.month)) + 1
-    months = 1 if months < 1
-    (current_balance.to_d / months).round(2)
   end
 
   def last_contribution_at