fix: resolve pythainlp and huggingface_hub Permission Denied errors by setting HOME and HF_HOME env variables, and add 'Try searching with AI' button to empty search state

Dockerfile

@@ -16,6 +16,9 @@ RUN npm run build
 # ── Stage 2: Python backend + serve ──
 FROM python:3.11-slim
 
+ENV HOME=/tmp
+ENV HF_HOME=/tmp/hf_home
+
 WORKDIR /app
 
 # Install system dependencies (for sentence-transformers / torch)

webapp/tipitaka-web/src/components/layout/NavDrawer.tsx

@@ -526,9 +526,32 @@ const NavDrawer: React.FC = () => {
               )}
 
               {!isLoading && results.length === 0 && query && (
-                <div className="text-center py-16 opacity-40">
-                  <Search size={36} className="mx-auto mb-3 opacity-20" />
-                  <p className="text-sm">ไม่พบ «{query}»</p>
+                <div className="text-center py-12 space-y-4">
+                  <div className="opacity-40">
+                    <Search size={36} className="mx-auto mb-3 opacity-20" />
+                    <p className="text-sm">ไม่พบ «{query}»</p>
+                  </div>
+                  
+                  {searchMode === 'fts' && (
+                    <div className="pt-2 px-4">
+                      <button
+                        type="button"
+                        onClick={() => performAiSearch()}
+                        disabled={isAiLoading}
+                        className={`w-full flex items-center justify-center gap-2 py-2.5 px-4 rounded-xl border text-sm font-bold transition-all ${
+                          isAiLoading
+                            ? `${s.border} opacity-60 cursor-not-allowed ${s.text}`
+                            : `border-purple-500/40 text-purple-400 hover:bg-purple-500/10 hover:border-purple-500/70`
+                        }`}
+                      >
+                        {isAiLoading ? (
+                          <><Loader2 size={14} className="animate-spin" /> กำลังค้นหาด้วย AI…</>
+                        ) : (
+                          <><Sparkles size={14} /> ลองค้นหาความหมายด้วย AI</>
+                        )}
+                      </button>
+                    </div>
+                  )}
                 </div>
               )}
             </div>