MPDX-9866 Disable all inputs of read-only goal calculations

[wjames111]

Description

• Depends on CruGlobal/mpdx_api#3472, which adds the GoalCalculation.readOnly field and rejects all mutations (including deletion) against read-only goals. Read-only goals are created automatically when a new staff member reports (MPDX-9865).
• Fetch the new readOnly field in the goal calculator and goals list queries, and expose isReadOnly through GoalCalculatorContext.
• Disable every input of a read-only goal while still showing the inputs and calculated totals: all autosave fields (via the central useGoalAutoSave hook), the SECA status select, the geographic location autocomplete, budget grid cell editing, Add Line Item and delete line-item actions, the Lump Sum/Line Item mode toggle, and the lump sum total field.
• Guard the two effects that fire mutations automatically (incompatible benefits plan clearing and default line-item repopulation) so they don't run against read-only goals.
• Hide the Delete button and show a "Read-Only" chip on read-only goal cards in the goals list (GoalCard.onDelete is now optional).
• Related Jira: MPDX-9866, MPDX-9865

Note: until the API PR reaches staging, yarn gql on this branch needs a staging schema snapshot with readOnly grafted on (API_URL=<snapshot file> yarn gql).

Testing

• Mark a goal calculation as read-only (until MPDX-9865's conversion is live, set it directly: UPDATE goal_calculations SET read_only = true WHERE id = '...' on staging, or mock readOnly: true locally)
• Go to HR Tools → Goal Calculator
• Check that the read-only goal's card shows a "Read-Only" chip and no Delete button, while other goals still have one
• Open the read-only goal with View
• Check that every field in Calculator Settings (goal name, personal, financial) is disabled but still shows its saved value
• Check that in Household/Ministry Expenses the Lump Sum/Line Item toggle and Add Line Item are disabled, rows can't be edited by double-clicking, no delete icons appear on hover, and category totals still display
• Check that the Summary Report still renders the calculated totals
• Open a normal (non-read-only) goal and check everything is still editable

Checklist:

• I have given my PR a title with the format "MPDX-(JIRA#) (summary sentence max 80 chars)"
• I have applied the appropriate labels (Add the label "Preview" to automatically create a preview environment)
• I have run the Claude Code /pr-review command locally and fixed any relevant suggestions
• I have requested a review from another person on the project
• I have tested my changes in preview or in staging
• I have cleaned up my commit history

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