ux(goals/show): catch-up CTA pre-fills + secondary "Adjust your target" link

The "Add $1,531.25" CTA used to open the contribution modal with an
empty amount field — label was a hint, not a default. Now passes the
catch-up amount via ?amount= and the contributions controller seeds
@contribution.amount from params. One click brings the user to the
modal already populated.

Adds a secondary text link below the primary CTA: "Or adjust your
target" → opens the edit modal (Turbo frame). Behavioural-econ choice
architecture: gives the rebaseline path explicitly so users who can't
realistically catch up don't feel forced into the contribution.

Trade-off: lets the alert respect autonomy — commit or recalibrate,
both fine. Action paralysis kept low by visual hierarchy (primary
button vs muted text link).

app/controllers/goal_contributions_controller.rb

@@ -7,7 +7,8 @@ class GoalContributionsController < ApplicationController
     @contribution = @goal.goal_contributions.new(
       contributed_at: Date.current,
       currency: @goal.currency,
-      source: "manual"
+      source: "manual",
+      amount: params[:amount].presence
     )
   end