AdminController: Rewrite avgTurnaround query to fetch approved times to
memory before computing TotalHours — EF Core/Npgsql cannot translate
TimeSpan.TotalHours to SQL, causing a 409 on every dashboard load.
ProposalService.ReviseAsync: Append -R{n} suffix to revision's
ProposalNumber so it doesn't violate the unique index. Previously copied
the parent's number verbatim, causing a DbUpdateException (500).
ProposalService Update/Approve/MarkSent: Add .Include(p => p.SubmittedBy)
(and ApprovedBy where relevant) so MapToResponse returns submittedByName
instead of null. GetByIdAsync already had these includes.