v1.16.4 — Per-phase tabs on "What's killing us"

Frontend-only (web/src/Home.jsx WipeMechanicsSection). Added a row of phase chips above the mechanic table: All (N), P0 (n), P1 (n), …, plus Unknown (n) if any mechanics aren't phase-labeled. All is the default (matches the prior view). Clicking a phase filters the table to mechanics tagged with that fight_model_phase. Phase counts in each tab label show that phase's total death count so you can see at a glance where the prog wall is. Per-phase filter persists until you switch encounters. Tab row hidden when only one phase has data.

If a selected phase has zero attributable deaths, the table area shows a "No attributable deaths in this phase yet" hint with the chips still visible so you can pick another phase. No backend change — uses the existing fight_model_phase field already on each cartography bucket.