feat(questions): make brand questions the primary monitoring & template axis

- add /questions/combination-fill endpoint with AI-driven, IP-region-aware matrix fill
- extract ip2region resolver from ops/app into shared/ipregion for cross-service use
- thread question_id filter through dashboard composite, citation summary, and collect-now
- switch template wizard from keyword inputs to brand-question selection (primary + supplemental)
- pass brand_question and supplemental_questions through assist/title/outline prompts
- add AiWaitingModal + 45s client timeout and request_timeout error mapping for long AI flows

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/transport/question_expansion_handler.go

@@ -36,6 +36,24 @@ func (h *QuestionExpansionHandler) CombinationPreview(c *gin.Context) {
 	response.Success(c, data)
 }
 
+func (h *QuestionExpansionHandler) CombinationFill(c *gin.Context) {
+	brandID, ok := parseBrandIDParam(c)
+	if !ok {
+		return
+	}
+	var req app.QuestionCombinationFillRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.Error(c, response.ErrBadRequest(40001, "invalid_params", err.Error()))
+		return
+	}
+	data, err := h.svc.FillQuestionCombination(c.Request.Context(), brandID, c.ClientIP(), req)
+	if err != nil {
+		response.Error(c, err)
+		return
+	}
+	response.Success(c, data)
+}
+
 func (h *QuestionExpansionHandler) AIDistill(c *gin.Context) {
 	brandID, ok := parseBrandIDParam(c)
 	if !ok {