mir-backend-beam-phoenix

Make It Right (Phoenix module). Phoenix + LiveView + Ecto + Plug + PostgreSQL specific reliability augmentation. Chains: mir-backend (generic gates) -> mir-backend-beam (BEAM runtime) -> this (Phoenix/LiveView/Ecto/Plug library mechanics). Adds the mechanical footguns the framework-agnostic tiers omit: LiveView per-connection process memory, with streams vs temporary_assigns for large collections; the async-assign…