feat(fusion_accounting_assets): asset disposal record model

- 4 disposal types: sale, scrap, donation, lost
- mail.thread tracking on type / date / sale amount / partner
- gain_loss_amount computed:
    - sale: sale_amount - book_value_at_disposal
    - scrap / donation / lost: -book_value_at_disposal (full loss)
- ondelete='restrict' on asset_id (cannot delete an asset with disposal)
- move_id placeholder for engine-created journal entry
- 4 new tests (59 total)

Made-with: Cursor

fusion_accounting_assets/models/__init__.py

@@ -1,3 +1,4 @@
 from . import fusion_asset_category
 from . import fusion_asset
 from . import fusion_asset_depreciation_line
+from . import fusion_asset_disposal

fusion_accounting_assets/models/fusion_asset_disposal.py

@@ -0,0 +1,56 @@
+"""Asset disposal records (sale, scrap, donation)."""
+
+from odoo import api, fields, models
+
+
+DISPOSAL_TYPES = [
+    ('sale', 'Sale'),
+    ('scrap', 'Scrap'),
+    ('donation', 'Donation'),
+    ('lost', 'Lost / Stolen'),
+]
+
+
+class FusionAssetDisposal(models.Model):
+    _name = "fusion.asset.disposal"
+    _description = "Asset Disposal Record"
+    _order = "disposal_date desc, id desc"
+    _inherit = ['mail.thread']
+
+    asset_id = fields.Many2one(
+        'fusion.asset', required=True, ondelete='restrict', tracking=True,
+    )
+    company_id = fields.Many2one(related='asset_id.company_id', store=True)
+    currency_id = fields.Many2one(related='asset_id.currency_id', store=True)
+
+    disposal_type = fields.Selection(
+        DISPOSAL_TYPES, required=True, default='sale', tracking=True,
+    )
+    disposal_date = fields.Date(
+        required=True, default=fields.Date.today, tracking=True,
+    )
+    sale_amount = fields.Monetary(
+        default=0.0, tracking=True,
+        help="Cash received (for sale disposal type).",
+    )
+    sale_partner_id = fields.Many2one('res.partner', tracking=True)
+
+    book_value_at_disposal = fields.Monetary(
+        readonly=True,
+        help="Asset book value at disposal date.",
+    )
+    gain_loss_amount = fields.Monetary(compute='_compute_gain_loss', store=True)
+    notes = fields.Text()
+
+    move_id = fields.Many2one(
+        'account.move', readonly=True, copy=False,
+        help="Journal entry created for this disposal.",
+    )
+
+    @api.depends('sale_amount', 'book_value_at_disposal', 'disposal_type')
+    def _compute_gain_loss(self):
+        for d in self:
+            if d.disposal_type == 'sale':
+                d.gain_loss_amount = d.sale_amount - d.book_value_at_disposal
+            else:
+                d.gain_loss_amount = -d.book_value_at_disposal