feat(e2e): add distributed E2E test framework with parametric traffic generation

Add run-e2e-test.sh with CLI parameters (--hits, --http-ratio, --dns, --tls,
--src-ips, --keep-analysis, --up) for configurable traffic generation. Traffic
runs from VM endpoints with multiple source IPs (alias IPs on eth0) to produce
distinct sessions for the ML pipeline. Fix curl TLS flags (--tlsv1.2 instead
of --tls-v1-2), skip redundant local verification in distributed mode, and
fix dashboard is_available() cache that never retried after ClickHouse recovery.

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

services/dashboard/backend/main.py

@@ -4,15 +4,28 @@ from __future__ import annotations
 
 import logging
 
-from fastapi import FastAPI
+from fastapi import FastAPI, Request
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import HTMLResponse, JSONResponse
 from fastapi.staticfiles import StaticFiles
+from fastapi.templating import Jinja2Templates
 
+from backend.database import ClickHouseUnavailable, is_available
 from backend.routes.api import router as api_router
 from backend.routes.pages import router as pages_router
 
 logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(name)s: %(message)s")
 
+_templates = Jinja2Templates(directory="backend/templates")
+
+_PAGE_MAP = {
+    "/": "overview", "/detections": "detections", "/scores": "scores",
+    "/traffic": "traffic", "/classify": "classify", "/features": "features",
+    "/models": "models", "/network": "network", "/campaigns": "campaigns",
+    "/tactics": "tactics", "/reflists": "reflists", "/fleet": "fleet",
+    "/health": "health", "/browsers": "browsers", "/fingerprints": "fingerprints",
+}
+
 app = FastAPI(title="JA4 SOC Dashboard", version="1.0.0")
 
 # CORS — allow all origins for dashboard access
@@ -24,6 +37,29 @@ app.add_middleware(
     allow_headers=["*"],
 )
 
+
+@app.exception_handler(ClickHouseUnavailable)
+async def ch_unavailable_handler(request: Request, exc: ClickHouseUnavailable):
+    """Return 503 for API calls, render degraded pages for HTML requests."""
+    accept = request.headers.get("accept", "")
+    path = request.url.path
+
+    # If the client expects JSON (API call), return 503 JSON
+    if "application/json" in accept or path.startswith("/api/"):
+        return JSONResponse(
+            status_code=503,
+            content={"detail": "ClickHouse unavailable", "error": str(exc)},
+        )
+
+    # For HTML pages, render the template with ch_available=False
+    page_name = _PAGE_MAP.get(path, "overview")
+    return _templates.TemplateResponse(
+        f"{page_name}.html",
+        {"request": request, "active_page": page_name, "ch_available": False},
+        status_code=503,
+    )
+
+
 # Static assets
 app.mount("/static", StaticFiles(directory="backend/static"), name="static")
 
@@ -32,6 +68,7 @@ app.include_router(api_router)
 app.include_router(pages_router)
 
 
-@app.get("/health")
-async def health():
-    return {"status": "ok"}
+@app.get("/api/healthcheck")
+async def healthcheck():
+    ch = is_available()
+    return {"status": "ok" if ch else "degraded", "clickhouse": "up" if ch else "down"}