fix(portal): correct terminology — Sales Orders everywhere (revert Purchase Orders rename)

The customer's Purchase Order is the doc they send US — a separate
artifact, often a PDF attachment on the quote. What lives in our
system is the Sales Order we create in response. Labeling the SO
list as "Purchase Orders" in the customer portal was a wrong-side
mapping.

Reverts and renames in this commit:

- Sidebar item label: "Purchase Orders" → "Sales Orders" (key stays
  odoo_orders; URL still /my/orders). _FP_SIDEBAR_LAYOUT.

- Dashboard KPI tile: "Active POs" → "Active Sales Orders". Link
  hint: "View POs →" → "View orders →". Link target updated to the
  current /my/orders (the legacy /my/purchase_orders still redirects
  but we point at the canonical URL now).

- Dashboard panel: "Recent Purchase Orders" → "Recent Sales Orders".
  Empty state: "No purchase orders yet." → "No sales orders yet."
  View-all link target updated to /my/orders.

- Dashboard docs entries strip: "Purchase Orders" docs entry title
  → "Sales Orders"; URL → /my/orders.

- Removed the three Odoo template rename inherits from
  fp_sale_order_portal.xml (sale.portal_my_home_menu_sale,
  sale.portal_my_orders, sale.sale_order_portal_content). With those
  gone the stock templates emit Odoo's native "Sales Order(s)" and
  "Your Orders" wording on the list page header, breadcrumb, and
  detail page <h2> — which is now the correct terminology.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_portal/controllers/portal.py

@@ -126,7 +126,7 @@ class FpCustomerPortal(CustomerPortal):
         {'type': 'section_label', 'label': 'Activity'},
         {'type': 'item',          'key': 'fp_quote_requests', 'label': 'Quote Requests',   'icon': '📄', 'url': '/my/quote_requests'},
         {'type': 'item',          'key': 'fp_configurator',   'label': 'Get a Quote',      'icon': '+',  'url': '/my/configurator'},
-        {'type': 'item',          'key': 'odoo_orders',       'label': 'Purchase Orders',  'icon': '🛒', 'url': '/my/orders'},
+        {'type': 'item',          'key': 'odoo_orders',       'label': 'Sales Orders',     'icon': '🛒', 'url': '/my/orders'},
         {'type': 'item',          'key': 'fp_jobs',           'label': 'Work Orders',      'icon': '⚙️', 'url': '/my/jobs'},
         {'type': 'section_label', 'label': 'Documents'},
         {'type': 'item',          'key': 'fp_certifications', 'label': 'Certifications',   'icon': '📑', 'url': '/my/certifications'},