fix(evaluations): correct fallback rounds + friendlier error messages

- Fallback names now use hyphens matching live API (carbanak-fin7, wizard-spider-sandworm)
- Add APT3 (R1) and Enterprise 2025/er7 (R7) to fallback - verified from live API
- Remove OilRig (R6) from fallback - CrowdStrike did not participate in Round 6
- Orange fallback banner only shows when NO rounds are available at all
- Soft gray note when rounds are loaded but API had transient error
- Check-new and import errors: detect 502/Cloudflare messages and show user-friendly text
  instead of raw Cloudflare HTML error messages

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

backend/app/services/attck_evaluations_service.py

@@ -64,10 +64,20 @@ _HEADERS = {
 
 # ---------------------------------------------------------------------------
 # Fallback: hardcoded public CrowdStrike ENTERPRISE rounds
-# Used when evals.mitre.org API is unreachable (Cloudflare, outage, etc.)
-# These are well-known, publicly documented rounds — safe to hardcode.
+# Used when evals.mitre.org API is unreachable (Cloudflare 502, outage, etc.)
+#
+# Names use the EXACT slugs the live API returns (hyphens, not underscores).
+# Verified from live API response on 2025-06-05.
+# CrowdStrike did NOT participate in Round 6 (OilRig) — not included.
 # ---------------------------------------------------------------------------
 _FALLBACK_ROUNDS: list[dict[str, Any]] = [
+    {
+        "name": "apt3",
+        "display_name": "APT3",
+        "eval_round": 1,
+        "domain": "ENTERPRISE",
+        "status": "PUBLIC",
+    },
     {
         "name": "apt29",
         "display_name": "APT29",
@@ -76,14 +86,14 @@ _FALLBACK_ROUNDS: list[dict[str, Any]] = [
         "status": "PUBLIC",
     },
     {
-        "name": "carbanak_fin7",
+        "name": "carbanak-fin7",
         "display_name": "Carbanak+FIN7",
         "eval_round": 3,
         "domain": "ENTERPRISE",
         "status": "PUBLIC",
     },
     {
-        "name": "wizard_spider_sandworm",
+        "name": "wizard-spider-sandworm",
         "display_name": "Wizard Spider + Sandworm",
         "eval_round": 4,
         "domain": "ENTERPRISE",
@@ -97,9 +107,9 @@ _FALLBACK_ROUNDS: list[dict[str, Any]] = [
         "status": "PUBLIC",
     },
     {
-        "name": "oilrig",
-        "display_name": "OilRig",
-        "eval_round": 6,
+        "name": "er7",
+        "display_name": "Enterprise 2025",
+        "eval_round": 7,
         "domain": "ENTERPRISE",
         "status": "PUBLIC",
     },