feat(fusion_accounting_documents): Documents app <-> invoice bridge

Replaces Enterprise's documents_account with a Fusion-native bridge.
When a PDF/image lands in the Documents app, users can convert it
into a draft vendor bill via a wizard that copies the document's
binary onto the new account.move and posts a chatter note linking
back to the source document.

Adds:
- documents.document.move_id (Many2one to the linked invoice)
- documents.document.is_invoice_candidate (computed; True for
  unlinked PDF/image binaries)
- documents.document.action_create_invoice() opens the wizard
- account.move.source_document_ids reverse linkage + statinfo button
- fusion.create.invoice.from.document.wizard (TransientModel + form)
- ir.actions.server bound to documents.document so the workflow
  appears in the kanban/list Actions menu (the Documents app has
  no regular form view to inherit from in v19)

The wizard:
- defaults to the company's first purchase journal
- supports vendor bill or vendor credit note
- copies the source attachment onto the new move
- posts a chatter note linking back
- marks the document linked so it stops appearing as a candidate

Auto-installs when documents + fusion_accounting_core are both
present. 8 unit tests cover the candidate flag, wizard happy path,
attachment copy, reverse linkage, already-linked guard, non-PDF
guard, and credit-note creation.

Made-with: Cursor

fusion_accounting_documents/models/documents_document.py

@@ -0,0 +1,71 @@
+"""Bridge documents.document to accounting moves.
+
+Adds a Many2one link to the created invoice/move, a computed
+``is_invoice_candidate`` flag for PDFs/images that have not yet been
+turned into a vendor bill, and the ``action_create_invoice`` entry
+point used by both the form button and the server action.
+"""
+
+from odoo import _, api, fields, models
+from odoo.exceptions import UserError
+
+
+INVOICE_CANDIDATE_MIMETYPES = (
+    'application/pdf',
+    'image/png',
+    'image/jpeg',
+    'image/jpg',
+)
+
+
+class DocumentsDocument(models.Model):
+    _inherit = 'documents.document'
+
+    move_id = fields.Many2one(
+        'account.move',
+        string='Linked Invoice/Move',
+        copy=False,
+        ondelete='set null',
+        help="The accounting move this document was used to create.",
+    )
+    is_invoice_candidate = fields.Boolean(
+        string='Is Invoice Candidate',
+        compute='_compute_is_invoice_candidate',
+        store=True,
+        help="True when this document looks like a vendor bill "
+             "(PDF/image binary) and has not yet been linked to a move.",
+    )
+
+    @api.depends('mimetype', 'type', 'move_id')
+    def _compute_is_invoice_candidate(self):
+        for d in self:
+            d.is_invoice_candidate = (
+                d.type == 'binary'
+                and (d.mimetype or '') in INVOICE_CANDIDATE_MIMETYPES
+                and not d.move_id
+            )
+
+    def action_create_invoice(self):
+        """Open the wizard to create a vendor invoice from this document."""
+        self.ensure_one()
+        if self.move_id:
+            raise UserError(_(
+                "This document is already linked to invoice %s.",
+                self.move_id.display_name,
+            ))
+        if self.type == 'folder':
+            raise UserError(_(
+                "Folders cannot be turned into invoices."
+            ))
+        if (self.mimetype or '') not in INVOICE_CANDIDATE_MIMETYPES:
+            raise UserError(_(
+                "Only PDF or image documents can be turned into invoices."
+            ))
+        return {
+            'type': 'ir.actions.act_window',
+            'name': _('Create Invoice from Document'),
+            'res_model': 'fusion.create.invoice.from.document.wizard',
+            'view_mode': 'form',
+            'target': 'new',
+            'context': {'default_document_id': self.id},
+        }