refactor(goals): use semantic color tokens for ring + status callout

`Goals::CardComponent#ring_color` and `goals/_status_callout` reached
into the Tailwind palette directly (`text-yellow-700`,
`var(--color-green-600)`, etc.) for status-coded colors. The
sure-design-system already exposes the matching semantic tokens
(`text-warning`, `text-success`, `--color-success`, `--color-warning`),
which theme-swap correctly in dark mode and survive palette renames
without view edits.

- `ring_color`: collapse `:reached` / `:on_track` to `--color-success`
  (the status pill already differentiates them via icon — completed star
  vs check) and `:behind` to `--color-warning`. The `:no_target_date`
  fallback keeps `--color-gray-400` for now since there's no semantic
  neutral token; that gets cleaned up alongside the DS::ProgressRing
  extraction.
- `_status_callout`: drop `text-yellow-700 theme-dark:text-yellow-300`
  and `text-green-700 theme-dark:text-green-300` for the equivalent
  semantic `text-warning` / `text-success` utilities.

No visual regression in light mode (success collapses two adjacent
greens into one); dark mode now properly inverts via the design
system's theme variants instead of hand-rolled overrides.

The `stroke="var(--budget-unused-fill)"` track on the inline card ring
stays for now — that's a token-rename refactor that touches budget
code outside this PR's scope and lands cleanest with the DS::ProgressRing
primitive that consolidates the three ring implementations.

app/components/goals/card_component.rb

@@ -15,9 +15,8 @@ class Goals::CardComponent < ApplicationComponent
 
   def ring_color
     case goal.status
-    when :reached then "var(--color-green-600)"
-    when :behind then "var(--color-yellow-600)"
-    when :on_track then "var(--color-green-500)"
+    when :reached, :on_track then "var(--color-success)"
+    when :behind then "var(--color-warning)"
     else "var(--color-gray-400)"
     end
   end

app/views/goals/_status_callout.html.erb

@@ -4,9 +4,9 @@
 
   variant_classes = case goal.status
                     when :behind
-                      "bg-warning/10 border-warning/20 text-yellow-700 theme-dark:text-yellow-300"
+                      "bg-warning/10 border-warning/20 text-warning"
                     when :on_track
-                      "bg-success/10 border-success/20 text-green-700 theme-dark:text-green-300"
+                      "bg-success/10 border-success/20 text-success"
                     else
                       "bg-surface-inset border-secondary text-secondary"
                     end