feat(goals): v2 architecture — drop ledger, derive balance, add pledge

Reshape the goals feature to live on top of linked-account balances.
A goal's balance is now the live balance of every depository account
linked to it — no parallel ledger, no "log a contribution" step.

The "Add contribution" affordance is replaced by a 7-day GoalPledge
(kind: transfer | manual_save). GoalPledge::Reconciler matches incoming
Transactions (via Account::ProviderImportAdapter) and Valuations (via
Account::ReconciliationManager) against open pledges within ±5 days,
±$0.50, or ±1% — single hook covers every provider (Plaid, SimpleFIN,
Lunchflow, Enable Banking, Brex, IBKR, Kraken, SnapTrade) plus manual
balance edits. A 15-minute Sidekiq cron sweeps expired pledges.

Goal model: balance derived from linked_accounts.sum(&:balance), new
pace (90-day net non-transfer inflow), months_of_runway,
last_matched_pledge_*, pledge_action_label_key (the "I just
transferred…" vs "I just saved…" verb switch).

UI:
- Index gets a 3-card KPI strip (Contributed last 30d / Needs this
  month / On track) plus a pending-pledges callout.
- Show page swaps the "Add contribution" CTA for the pledge modal,
  replaces the contribution list with a pending-pledge banner, and
  rebuilds the funding widget into per-account rows with a 12-bucket
  weekly sparkline and last-30 inflow.
- Projection chart adds a required-line (dashed light from
  today → target) and a translucent pending-pledge bump at today's X.

Schema (3 migrations):
1. goal_pledges table with PG enums (goal_pledge_kind, goal_pledge_status),
   open-by-expiry index, and unique-when-not-null matched_transaction_id.
2. Drop goal_contributions.
3. Partial unique index on
   transactions ((extra -> 'goal' ->> 'pledge_id')) built CONCURRENTLY
   so it doesn't block prod.

After pulling: run bin/rails db:migrate, then commit the schema.rb sync
separately (or let CI regenerate).

Deferred to v1.1: allocation columns, contention/archived banners,
"why is this behind?" diagnostic, reallocate flow, refresh-sync +
Plaid throttle, unallocated-cash chip, joint-account approval,
goal_activities log, polymorphic matched_entry_id/type for manual
pledge audit.

test/controllers/goals_controller_test.rb

@@ -49,25 +49,6 @@ class GoalsControllerTest < ActionDispatch::IntegrationTest
     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: {