[16.0][IMP] budget_project: add budget.project reservation model for kmitl_project

[n3n]

Summary

• Introduce budget.project as an intermediary reservation model between budget.appropriation and kmitl.project, separating budget allocation from project approval workflows
• On posting an appropriation, a budget.project reservation is created (instead of directly creating kmitl.project), storing name, budget amount, budget account, fiscal year, and analytic dimensions
• Users can link an existing kmitl.project via dropdown or create one directly from the reservation using the "สร้างโครงการ/กิจกรรม" button; linking triggers analytic account creation and injects the kmitl_project dimension into budget.move.line.analytic_distribution
• Adds a dedicated menu "การกันเงินโครงการ/กิจกรรม" with tree/form views and matched/unmatched filters for tracking reservation status

Test plan

• Post a budget.appropriation with a line where enable_project=True and verify a budget.project record is created
• Verify budget.move.line has budget_project_id but no kmitl_project analytic dimension yet
• Use "สร้างโครงการ/กิจกรรม" button to create a kmitl.project from the reservation; verify data is copied and analytic account is created
• Link an existing kmitl.project via dropdown and verify budget.move.line.analytic_distribution includes the project dimension
• Verify chatter messages appear on both budget.project and kmitl.project
• Verify kmitl.project.is_editable = False once linked

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