chore: reconcile duplicate milestone schemes (M0–M7 vs M1–M4 descriptive)

[yves-vogl]

Problem

The repo has two parallel milestone schemes that coexist:

• Scheme A (milestones 1–8): M0 — Bootstrap, M1 — DSP Core, M2 — Dynamics, M3 — Distortion Engine, M4 — EQ & IR Loader, M5 — State & Presets, M6 — GUI, M7 — Release Engineering. Used by issues Scaffold CMake build system (JUCE 8.0.14 via CPM, SharedCode pattern) #1–Windows packaging (zip) #32.
• Scheme B (milestones 9–12): M1 — DSP completion & test coverage, M2 — Presets & state recall, M3 — GUI & accessibility, M4 — Release: signing, notarization, v1.0.0. Used by issues User manual (docs/manual.md) #33–Release engineering: tagged releases + installers #48.

M1–M4 mean different things in each scheme, so milestone filtering / roadmap views are ambiguous.

Decision needed (yves-decision)

Pick one canonical scheme, migrate issues to it, and close/delete the redundant milestones. Scheme A matches the M0–M7 roadmap in project memory and the DSP/GUI/Release breakdown; Scheme B looks like a later re-cut.

Acceptance criteria

• One canonical milestone set remains.
• Every open issue is reassigned to the correct canonical milestone.
• Redundant milestones are closed/deleted.