fix(security): resolve Critical+High findings from module audit — agent, translate, superset_client

P0 — CRITICAL (CWE-798): JWT_SECRET crash-early
  Replace hardcoded super-secret-key fallback with os.environ["JWT_SECRET"]
  and ${JWT_SECRET:?} syntax in app.py + docker-compose files

P1 — HIGH: Frontend dependency CVEs
  Upgrade svelte 5.43.8 → 5.56.4 — resolves devalue DoS (GHSA-g2pg-6438-jwpf)
  and svelte XSS (GHSA-crpf-4hrx-3jrp, GHSA-m56q-vw4c-c2cp, GHSA-rcqx-6q8c-2c42)

P2 — MEDIUM: Logging hygiene + contract gaps + tool resolver refactor
  Apply _redact_sensitive_fields() in middleware + event streaming
  Truncate LLM error body to 100 chars
  Add @RATIONALE/@REJECTED to HandleResume + SaveConversation
  Refactor deterministic intent matching → LLM-driven tool resolution

P3 — LOW: Translate logging hardening
  Move _sanitize_url() to _utils.py (shared, no circular imports)
  Sanitize base_url before logging in _llm_call.py and _llm_async_http.py
  Emit EXPLORE warning when LLM_SSL_VERIFY=false disables TLS

superset_client module: passed clean — no changes needed

frontend/package.json

@@ -31,7 +31,7 @@
     "globals": "^16.0.0",
     "jsdom": "^28.1.0",
     "postcss": "^8.4.0",
-    "svelte": "^5.43.8",
+    "svelte": "^5.56.4",
     "tailwindcss": "^3.0.0",
     "typescript-eslint": "^8.60.1",
     "vite": "^7.2.4",