feat(fusion_accounting_migration): add Enterprise uninstall safety guard + wizard skeleton

Phase 0 Task 17. Installs a safety guard on ir.module.module that blocks
uninstall of Odoo Enterprise accounting modules (account_accountant,
account_reports, accountant, account_followup, account_asset,
account_budget, account_loans) until the per-module migration flag
fusion_accounting.migration.<name>.completed is set to True. Guard
covers both button_immediate_uninstall (UI) and module_uninstall
(CLI/API) paths, raising UserError with a pointer to the migration
wizard and an escape hatch config parameter.

Also ships a TransientModel fusion.migration.wizard as a shell: it
detects installed Enterprise modules via GUARDED_MODULES and exposes
action_run_migration for sub-modules to extend in later phases. No
per-feature migrations are registered yet -- Phase 1+ sub-modules will
hook in their own steps.

Tests: TestSafetyGuard x2 pass (blocked-when-pending verified with
account_accountant installed; not-blocked-when-completed verified by
setting the flag).

Made-with: Cursor

fusion_accounting_migration/wizards/__init__.py

@@ -0,0 +1 @@
+from . import migration_wizard

fusion_accounting_migration/wizards/migration_wizard.py

@@ -0,0 +1,65 @@
+"""Migration wizard skeleton.
+
+Per-feature migration logic (account.asset -> fusion.asset, etc.) is added
+by each fusion sub-module that replaces an Enterprise feature, by extending
+this wizard via _inherit.
+
+Phase 0 ships the wizard with no migrations registered. Phase 1 will add
+the bank-rec verification check. Phase 6 will add asset migration, etc.
+"""
+
+from odoo import _, api, fields, models
+
+
+class FusionMigrationWizard(models.TransientModel):
+    _name = "fusion.migration.wizard"
+    _description = "Migrate from Odoo Enterprise to Fusion Accounting"
+
+    enterprise_modules_detected = fields.Char(
+        compute='_compute_detected',
+        string="Enterprise Modules Detected",
+    )
+    notes = fields.Text(default=lambda self: self._default_notes())
+
+    def _default_notes(self):
+        return _(
+            "This wizard migrates data from Odoo Enterprise accounting modules "
+            "to Fusion Accounting tables. Run before uninstalling Enterprise. "
+            "After a successful run, each migrated module is marked complete "
+            "and the Enterprise uninstall safety guard will allow uninstall.\n\n"
+            "Phase 0 of the roadmap ships this wizard as a shell. As Phase 1, "
+            "Phase 5, Phase 6, etc. ship, each adds its own migration step here."
+        )
+
+    @api.depends_context('uid')
+    def _compute_detected(self):
+        Mod = self.env['ir.module.module'].sudo()
+        from ..models.ir_module_module import GUARDED_MODULES
+        installed = Mod.search([
+            ('name', 'in', list(GUARDED_MODULES)),
+            ('state', '=', 'installed'),
+        ])
+        for w in self:
+            w.enterprise_modules_detected = ', '.join(installed.mapped('name')) or _("None")
+
+    def action_run_migration(self):
+        """Stub: Phase 0 has no migrations to run.
+
+        Sub-modules extend this method to perform their per-module migration,
+        then set the corresponding fusion_accounting.migration.<name>.completed
+        config param to True.
+        """
+        return {
+            'type': 'ir.actions.client',
+            'tag': 'display_notification',
+            'params': {
+                'type': 'info',
+                'title': _("Nothing to migrate (yet)"),
+                'message': _(
+                    "Phase 0 ships the migration framework but no per-feature "
+                    "migrations are registered yet. Each fusion sub-module that "
+                    "replaces an Enterprise feature (Phase 1+) will register its "
+                    "own migration step here."
+                ),
+            },
+        }

fusion_accounting_migration/wizards/migration_wizard_views.xml

@@ -1,4 +1,28 @@
 <?xml version="1.0" encoding="utf-8"?>
 <odoo>
-    <!-- Migration wizard view stub. Populated in Task 17. -->
+    <record id="view_fusion_migration_wizard_form" model="ir.ui.view">
+        <field name="name">fusion.migration.wizard.form</field>
+        <field name="model">fusion.migration.wizard</field>
+        <field name="arch" type="xml">
+            <form string="Migrate from Enterprise">
+                <sheet>
+                    <group>
+                        <field name="enterprise_modules_detected" readonly="1"/>
+                        <field name="notes" readonly="1"/>
+                    </group>
+                </sheet>
+                <footer>
+                    <button name="action_run_migration" type="object" string="Run Migration" class="btn-primary"/>
+                    <button special="cancel" string="Close" class="btn-secondary"/>
+                </footer>
+            </form>
+        </field>
+    </record>
+
+    <record id="action_fusion_migration_wizard" model="ir.actions.act_window">
+        <field name="name">Migrate from Enterprise</field>
+        <field name="res_model">fusion.migration.wizard</field>
+        <field name="view_mode">form</field>
+        <field name="target">new</field>
+    </record>
 </odoo>