feat(iace/mitigations): is_relevant + is_customer_standard flags

[migration-approved]

Expert-driven workflow refinement on the Massnahmen page. The engine seeds
~80 mitigations per project, but for a concrete customer site most need a
relevance decision before they're meaningful in verification:

  status: 'planned' | 'implemented' | 'verified'   (existing — verification track)
  is_relevant          bool   (new)                (does this apply to *this* site?)
  is_customer_standard bool   (new)                (already in place at customer — no evidence)

Decision flow on the Mitigations tab:
  Engine-seeded → is_relevant=false (Default, waiting for expert)
  Expert checks "Relevant" → is_relevant=true → surfaces in verification
  Expert clicks trash       → DELETE (banner warns: do not click Reinit
                                       afterwards or seeds come back)
  In verification, customer_standard=true bypasses evidence upload

is_customer_standard implies is_relevant (DB CHECK constraint).

Migration 029_iace_mitigation_relevance.sql:
  ALTER TABLE iace_mitigations ADD COLUMN is_relevant ..., is_customer_standard ...
  + CHECK constraint + partial index on is_relevant for the verification
    page's filter.

Backend (Go):
  - Mitigation struct gains two bool fields
  - CreateMitigation: defaults to false/false (engine-seeded mitigations
    start unbewertet)
  - UpdateMitigation: new case clauses for both keys; setting
    is_customer_standard=true auto-flips is_relevant=true to satisfy
    the CHECK constraint
  - All three SELECT statements (ListMitigations, ListMitigationsByProject,
    getMitigation) extended with the two new columns

Frontend:
  - Maßnahmen-page columns: [Relev. ☑] [Lösch. 🗑] Title | #Hazards | P·I·V
  - Group-header checkbox shows tri-state (indeterminate when partial),
    flips all instances in the group at once
  - Banner above the table: "Markiere jede Maßnahme als Relevant oder
    lösche sie. Nach Löschen kein Neu initialisieren mehr drücken."
  - Relevant rows tinted emerald, customer-standard label visible
  - Legacy bulk-select state + helpers removed (the Relevant checkbox
    now IS the primary mass action)
  - useMitigations gains handleSetRelevant, handleSetCustomerStandard,
    handleDeleteSilent (for non-confirm bulk deletes)

Future use: is_customer_standard mitigations from a prior project at the
same customer can later be auto-suggested when commissioning the next
plant — turning expert knowledge into reusable customer-profile data.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

admin-compliance/app/sdk/iace/[projectId]/mitigations/_components/types.tsx

@@ -13,6 +13,9 @@ export interface Mitigation {
   verified_by: string | null
   source?: string
   operational_states?: string[]
+  // Expert flags (migration 029).
+  is_relevant?: boolean
+  is_customer_standard?: boolean
 }
 
 export interface Hazard {