refactor: rename Savings Goals feature to Goals

User-facing rename + structural rename. Feature is now called just
"Goals" everywhere — page title, sidebar nav, modal headings, flash
messages, AI assistant tool. Code identifiers follow:

- Models: SavingsGoal → Goal, SavingsContribution → GoalContribution,
  SavingsGoalAccount → GoalAccount.
- Tables: savings_goals → goals, savings_contributions → goal_contributions,
  savings_goal_accounts → goal_accounts. FK columns savings_goal_id →
  goal_id. New migration db/migrate/20260511100003_rename_savings_to_goals.rb
  uses rename_table + rename_column; PG handles index renaming and FK
  redirection automatically.
- Controllers: SavingsGoalsController → GoalsController,
  SavingsContributionsController → GoalContributionsController.
- Routes: /savings_goals → /goals, nested /goals/:id/contributions
  (resource name shifts; old route name aliases dropped).
- ViewComponent namespace: Savings::* → Goals::*. Component class
  names drop their redundant "Goal" prefix where the namespace already
  carries it: Savings::GoalCardComponent → Goals::CardComponent,
  Savings::GoalAvatarComponent → Goals::AvatarComponent. Others keep
  their names (Goals::ProgressRingComponent, Goals::StatusPillComponent,
  Goals::AccountStackComponent, Goals::FundingAccountsBreakdownComponent).
- Stimulus controllers: savings_goal_* → goal_*, savings_goals_filter
  → goals_filter. Stimulus identifiers in data-controller / data-*
  attributes follow.
- Locale keys: savings_goals: → goals: (top level), savings_contributions:
  → goal_contributions: (top level). All t() callers updated.
- AI assistant tool: Assistant::Function::CreateSavingsGoal →
  Assistant::Function::CreateGoal, tool name "create_savings_goal" →
  "create_goal", description / response text updated.
- Sidebar nav label "Savings" → "Goals". Goals/show + index page title
  "Savings" → "Goals". Empty goals_section heading/subtitle dropped
  (duplicated the page title post-rename).

Original migrations create_savings_goals / create_savings_goal_accounts /
create_savings_contributions remain untouched so historical replay
still works; the rename migration runs on top.

test/controllers/goals_controller_test.rb

@@ -0,0 +1,146 @@
+require "test_helper"
+
+class GoalsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    sign_in users(:family_admin)
+    @goal = goals(:vacation_italy)
+    @depository = accounts(:depository)
+    @connected = accounts(:connected)
+    ensure_tailwind_build
+  end
+
+  test "index renders with active filter by default" do
+    get goals_url
+    assert_response :success
+    assert_match(/Goals/i, response.body)
+  end
+
+  test "index honors state filter" do
+    get goals_url(state: "paused")
+    assert_response :success
+  end
+
+  test "show renders the goal" do
+    get goal_url(@goal)
+    assert_response :success
+    assert_match(@goal.name, response.body)
+  end
+
+  test "new renders the modal form" do
+    get new_goal_url
+    assert_response :success
+  end
+
+  test "create persists a goal with linked accounts" do
+    assert_difference -> { Goal.count } => 1,
+                      -> { GoalAccount.count } => 2 do
+      post goals_url, params: {
+        goal: {
+          name: "New goal",
+          target_amount: "1000",
+          target_date: 3.months.from_now.to_date.iso8601,
+          color: "#4da568",
+          account_ids: [ @depository.id, @connected.id ]
+        }
+      }
+    end
+
+    goal = Goal.order(created_at: :desc).first
+    assert_redirected_to goal_path(goal)
+  end
+
+  test "create with initial contribution writes the contribution" do
+    assert_difference -> { GoalContribution.count } => 1 do
+      post goals_url, params: {
+        goal: {
+          name: "Goal with initial",
+          target_amount: "1000",
+          color: "#4da568",
+          account_ids: [ @depository.id ],
+          initial_contribution_amount: "50",
+          initial_contribution_account_id: @depository.id
+        }
+      }
+    end
+
+    contribution = GoalContribution.order(created_at: :desc).first
+    assert_equal "initial", contribution.source
+    assert_equal 50, contribution.amount.to_i
+  end
+
+  test "create rejects missing account_ids" do
+    assert_no_difference "Goal.count" do
+      post goals_url, params: {
+        goal: {
+          name: "Bad goal",
+          target_amount: "1000",
+          color: "#4da568"
+        }
+      }
+    end
+    assert_response :unprocessable_entity
+  end
+
+  test "create rejects foreign accounts" do
+    other_family = Family.create!(name: "Other", currency: "USD", locale: "en", country: "US", timezone: "UTC")
+    foreign = Account.create!(family: other_family, accountable: Depository.new, name: "Foreign", currency: "USD", balance: 100)
+
+    assert_no_difference "Goal.count" do
+      post goals_url, params: {
+        goal: {
+          name: "Foreign goal",
+          target_amount: "1000",
+          color: "#4da568",
+          account_ids: [ foreign.id ]
+        }
+      }
+    end
+    assert_response :unprocessable_entity
+  end
+
+  test "update modifies identity fields" do
+    patch goal_url(@goal), params: { goal: { name: "Renamed" } }
+    assert_redirected_to goal_path(@goal)
+    assert_equal "Renamed", @goal.reload.name
+  end
+
+  test "pause/resume/complete/archive/unarchive flow" do
+    fresh = goals(:emergency_fund)
+    patch pause_goal_url(fresh)
+    assert fresh.reload.paused?
+    patch resume_goal_url(fresh)
+    assert fresh.reload.active?
+    patch complete_goal_url(fresh)
+    assert fresh.reload.completed?
+    patch archive_goal_url(fresh)
+    assert fresh.reload.archived?
+    patch unarchive_goal_url(fresh)
+    assert fresh.reload.active?
+  end
+
+  test "destroy on non-archived is rejected" do
+    assert_no_difference "Goal.count" do
+      delete goal_url(@goal)
+    end
+    assert_redirected_to goal_path(@goal)
+  end
+
+  test "destroy on archived deletes" do
+    @goal.archive!
+    assert_difference "Goal.count", -1 do
+      delete goal_url(@goal)
+    end
+    assert_redirected_to goals_path
+  end
+
+  test "another family's goal returns 404" do
+    other_family = Family.create!(name: "Other", currency: "USD", locale: "en", country: "US", timezone: "UTC")
+    other_account = Account.create!(family: other_family, accountable: Depository.new, name: "Foreign", currency: "USD", balance: 100)
+    other_goal = other_family.goals.new(name: "Foreign goal", target_amount: 100, currency: "USD")
+    other_goal.goal_accounts.build(account: other_account)
+    other_goal.save!
+
+    get goal_url(other_goal)
+    assert_response :not_found
+  end
+end