feat(phase4+5): role hierarchy, tenant config, fallback material, dead code removal

Phase 4.1 — Role Hierarchy:
  - UserRole enum: add global_admin (platform operator) + tenant_admin
    (per-tenant admin); keep legacy 'admin' for backward compat
  - Role sets: ADMIN_ROLES, TENANT_ADMIN_ROLES, PM_ROLES, RLS_BYPASS_ROLES
  - New auth guards: require_global_admin(), require_tenant_admin_or_above(),
    require_pm_or_above(), is_admin(), is_privileged()
  - Legacy require_admin / require_admin_or_pm now check both old+new roles
  - Migration 049: ADD VALUE global_admin + tenant_admin with AUTOCOMMIT
    workaround; backfills admin → global_admin
  - Seed: new admin users created with global_admin role

Phase 4.3 — RLS bypass updated for global_admin in get_db + set_tenant_context

Phase 4.4 — Tenant Feature Flags:
  - Migration 050: tenant_config JSONB on tenants table
  - Tenant model: tenant_config field + get_config() accessor
  - Defaults: max_concurrent_renders=3, fallback_material, invoice_prefix etc.

Phase 5.1 — Fallback Material:
  - blender_render.py: replace PALETTE_LINEAR/PALETTE_HEX/_assign_palette_material
    with _assign_failed_material() → SCHAEFFLER_059999_FailedMaterial (magenta)
  - Unmatched parts now logged explicitly before rendering

Phase 5.2 — Remove EEVEE fallback:
  - render_blender.py: EEVEE→Cycles silent retry removed; hard failure on EEVEE error

Phase 5.3 — Remove Blender version check:
  - render_blender.py: deleted MIN_BLENDER_VERSION = (5, 0, 1) constant

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/domains/auth/models.py

@@ -8,9 +8,27 @@ import enum
 
 
 class UserRole(str, enum.Enum):
+    # New role hierarchy (Phase 4)
+    global_admin = "global_admin"    # platform operator — bypasses RLS, all tenants
+    tenant_admin = "tenant_admin"    # per-tenant admin — full control within own tenant
+    project_manager = "project_manager"  # order/render management within tenant
+    client = "client"               # read own orders, create draft orders
+
+    # Legacy alias — kept for backward compat during migration; use global_admin for new code
     admin = "admin"
-    project_manager = "project_manager"
-    client = "client"
+
+
+# Roles that have administrative privileges (global_admin + legacy admin)
+ADMIN_ROLES = {"global_admin", "admin"}
+
+# Roles with tenant-level admin access
+TENANT_ADMIN_ROLES = {"global_admin", "tenant_admin", "admin"}
+
+# Roles with project management or above
+PM_ROLES = {"global_admin", "tenant_admin", "project_manager", "admin"}
+
+# Roles that bypass RLS (see TenantContextMiddleware + get_db)
+RLS_BYPASS_ROLES = {"global_admin", "admin"}
 
 
 class User(Base):