Proposal & payment workflow overhaul

[Copilot]

Replaces the multi-step proposal/approval process with a single canonical proposal object per customer request, with a linear flow: request → staff drafts proposal → customer views/accepts/requests changes → payment → work begins.

Data layer

• New data/payments.json store; portalLoadPayments/portalSavePayments helpers
• portalGenerateUniqueProposalId() / portalGenerateUniquePaymentId() (date-prefixed: PROP-YYYYMMDD-XXXX)
• Expanded PayPal settings in portalDefaultAdminSettings: nested sandbox/live credential sub-objects, mode enum (manual/sandbox/live), general fields (currency, payment_instructions, enable_webhook_logging, etc.)
• PORTAL_PAYPAL_WEBHOOK_LOG constant; backward-compat fallback reads old flat status field

Staff pages (new)

• staff/proposals.php — pipeline list with status badges, bulk actions
• staff/proposal-edit.php — full editor: all proposal fields, dynamic milestone support (0–5), contract-required toggle, save-draft / send-to-customer
• staff/proposal-view.php — read-only view with change requests panel
• staff/proposal-send.php — sets proposal_status=sent, stamps sent_at, fires email
• staff/payment-record.php — manual payment recorder; writes payments.json, advances proposal/milestone status

Client pages

• client/proposal-view.php — full detail view: accept form (with checkbox confirmation), request-changes form (stores into proposal.change_requests[]), conditional PayPal payment link based on configured mode
• client/proposals.php — updated with "How This Works" steps, status cards, highlighted call-to-action per status
• client/proposal.php — now a redirect to proposal-view.php

Proposal statuses

draft → sent → changes_requested → accepted → payment_pending → paid_start → in_progress → completed / cancelled

PayPal webhook placeholder

• paypal-webhook.php — logs raw POST payloads to data/paypal-webhook-log.json (gated on enable_webhook_logging), capped at 500 entries, returns 200. Stubbed TODOs for signature verification and transaction-to-proposal matching.

Settings UI (settings.php)

• PayPal section replaced: mode dropdown, separate Sandbox / Live credential cards, masked secrets (placeholder •••• shown after save; secret only overwritten on non-blank submit), general settings checkboxes

Dashboard (dashboard.php)

• Staff: Proposal Pipeline row (Draft / Sent / Changes Requested / Accepted / Awaiting Payment / Paid+Ready / In Progress) + quick-links (Proposals, + New Proposal, Record Payment)
• Client: "Proposals to Review" card (highlights amber when > 0), My Proposals count

[Copilot]

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