Set the search summary model from the settings panel

Summarizing web search results falls back to DEFAULT_MODEL, so a local Ollama
model ends up doing it and the call can fail — which surfaces only as
"保存できる要約なし" in the chat. Make SEARCH_SUMMARY_MODEL settable at runtime:
add it to the settings allowlist and read it from os.environ on each call
(knowledge._summary_model), the way LOCAL_KB_EMBEDDING_MODEL already works.
Importing it as a config constant would keep the old value until a restart.

Show the current value of the settings that are not secrets. A model name
rendered as ••••qwen3 gives no way to tell what is in effect, so the store now
marks those keys (NON_SECRET_KEYS) and returns them unmasked; the API field is
renamed masked -> display_value and carries a secret flag that the panel uses
to pick the input type, replacing the list it kept on its own side.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/components/SettingsPanel.vue

@@ -46,11 +46,9 @@ const KEY_LABELS: Record<string, string> = {
   OLLAMA_API_BASE: 'Ollama API Base URL',
   TAVILY_API_KEY: 'Tavily APIキー',
   LOCAL_KB_EMBEDDING_MODEL: '埋め込みモデル（ローカルナレッジベース検索用）',
+  SEARCH_SUMMARY_MODEL: '要約モデル（Web検索結果のまとめ用）',
 }
 
-// 秘匿情報ではないため、マスクせず通常のテキスト入力として表示するキー
-const PLAIN_TEXT_KEYS = new Set(['LOCAL_KB_EMBEDDING_MODEL', 'OLLAMA_API_BASE', 'AWS_REGION_NAME'])
-
 async function submitPassword() {
   const ok = await store.unlock(passwordInput.value)
   if (ok) passwordInput.value = ''
@@ -106,8 +104,8 @@ onMounted(() => {
         <div class="row">
           <input
             v-model="drafts[entry.key]"
-            :type="PLAIN_TEXT_KEYS.has(entry.key) ? 'text' : 'password'"
-            :placeholder="entry.is_set ? `設定済み ${entry.masked}` : '未設定'"
+            :type="entry.secret ? 'password' : 'text'"
+            :placeholder="entry.is_set ? `現在: ${entry.display_value}` : '未設定'"
             autocomplete="off"
           />
           <button