Release automation + contributor scaffolding

[codedpro]

Tag-triggered workflow attaching the compiled .ex5 (already produced by compile-ea.yml) to a GitHub Release; CONTRIBUTING.md + issue templates documenting the ASCII/CRLF rule for the .mq5 and CI expectations. Also: modernize pinned Python deps (fastapi 0.109 -> current; lifts the httpx<0.28 test pin).
From docs/ROADMAP.md.