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/services/render_blender.py

@@ -14,8 +14,6 @@ from pathlib import Path
 
 logger = logging.getLogger(__name__)
 
-MIN_BLENDER_VERSION = (5, 0, 1)
-
 
 def _glb_from_step(step_path: Path, glb_path: Path, quality: str = "low") -> None:
     """Convert STEP → GLB via OCC (export_step_to_gltf.py, no Blender needed).
@@ -226,12 +224,8 @@ def render_still(
 
     log_lines = [l for l in stdout_lines if "[blender_render]" in l]
 
-    # EEVEE fallback to Cycles on non-signal error
-    if returncode > 0 and engine == "eevee":
-        logger.warning("EEVEE failed (exit %d) — retrying with Cycles", returncode)
-        returncode, stdout_lines2, stderr_lines2 = _run("cycles")
-        engine_used = "cycles (eevee fallback)"
-        log_lines.extend(l for l in stdout_lines2 if "[blender_render]" in l)
+    # EEVEE fallback removed (Phase 5.2): EEVEE Next in Blender 5.0+ is stable.
+    # If EEVEE fails, it is a hard failure — no silent retry.
 
     if returncode != 0:
         stdout_tail = "\n".join(stdout_lines[-50:]) if stdout_lines else ""