chore(goals): drop dead V1 hooks + surface chart errors

Loose ends from the V1 → V2 refactor that the architecture commit
didn't sweep.

- Demo generator (B14): the `goal_spec[:contributions]` arrays
  + the `wedding_contribs` / `house_contribs` builders still
  shipped in the file, but the seeding loop that consumed them
  was deleted alongside `GoalContribution`. Dead data. Strip both
  the per-goal arrays and the two locals. Goal balance/pace in
  the demo family now derives from the linked depository
  accounts' own seeded entries elsewhere in the generator.

- Goal stepper controller (B16): the `static targets` declaration
  still listed `initialContributionAmount` and
  `initialContributionAccountSelect`, and `refreshAccountSelect`
  + its two callsites still ran every time a linked-account
  checkbox flipped. The HTML targets disappeared with the V2
  stepper rebuild, so `has*Target` guards short-circuited and the
  method was a no-op — but it was still dispatched on every
  change. Drop the targets, the method, and the two callsites.

- Chart series rescue (B25): `Goal#balance_series_values` and
  `FundingAccountsBreakdownComponent#sparkline_map` both swallowed
  `StandardError` with a `Rails.logger.warn(…)`. The chart then
  degraded to "target line only" silently. Promote the log to
  `error` level and forward to Sentry when present (matching the
  pattern in `Account::Syncer`, `Sync`, `PlaidItem`). Fallback to
  empty result still preserved so the surface degrades instead of
  500-ing.

app/javascript/controllers/goal_stepper_controller.js

@@ -3,8 +3,8 @@ import { Controller } from "@hotwired/stimulus";
 // 2-step modal stepper for creating a goal.
 //
 // Single <form> with two panels. Step 1 collects identity (name, amount,
-// date, color, notes, linked accounts). Step 2 reviews + optional initial
-// contribution. All state lives in the DOM — no half-records, single POST.
+// date, color, notes, linked accounts). Step 2 reviews and submits. All
+// state lives in the DOM — no half-records, single POST.
 export default class extends Controller {
   static targets = [
     "step1Panel",
@@ -22,8 +22,6 @@ export default class extends Controller {
     "amountError",
     "accountsError",
     "linkedAccountCheckbox",
-    "initialContributionAmount",
-    "initialContributionAccountSelect",
     "reviewName",
     "reviewSummary",
     "reviewSuggested",
@@ -85,7 +83,6 @@ export default class extends Controller {
     this.step1PanelTarget.classList.add("hidden");
     this.step2PanelTarget.classList.remove("hidden");
     this.updateStepperState();
-    this.refreshAccountSelect();
     this.updateReview();
     this.updateFooter();
   }
@@ -99,7 +96,6 @@ export default class extends Controller {
   }
 
   linkedAccountChanged() {
-    this.refreshAccountSelect();
     this.refreshSubmitState();
     this.updateReview();
     if (this.linkedAccountCheckboxTargets.some((cb) => cb.checked) && this.hasAccountsErrorTarget) {
@@ -169,26 +165,6 @@ export default class extends Controller {
     this.footerRightButtonTarget.classList.toggle("opacity-50", !anyChecked && this.currentStep === 1);
   }
 
-  refreshAccountSelect() {
-    if (!this.hasInitialContributionAccountSelectTarget) return;
-    const select = this.initialContributionAccountSelectTarget;
-    const previous = select.value;
-    while (select.options.length > 1) select.remove(1);
-
-    this.linkedAccountCheckboxTargets
-      .filter((cb) => cb.checked)
-      .forEach((cb) => {
-        const opt = document.createElement("option");
-        opt.value = cb.value;
-        opt.textContent = cb.dataset.accountName || cb.value;
-        select.appendChild(opt);
-      });
-
-    if ([...select.options].some((o) => o.value === previous)) {
-      select.value = previous;
-    }
-  }
-
   updateStepperState() {
     if (this.hasStep1CircleTarget) {
       this.step1CircleTarget.classList.toggle("bg-inverse", this.currentStep === 1);