整改一期：发布这条链路先跑顺

四条改动都在"发布一个代喂任务"这条路上：

定位拿不到不再把人卡死。地址可以不带坐标保存，界面标成"未核验定位"，
这条地址的打卡照常，只是不比对距离——总比逼着用户放弃发布要好。客户端
另外给了两条退路：去系统设置开权限，或者地图选点。

价格从写死的 30 元改成服务端按物种、城市、每次时长算的推荐价，规则放在
配置里，运营改一次不用等发版；用户改过之后就以他填的为准，不再被覆盖。

发布与支付并成一步：底部常驻"合计 ¥x = n 次 × ¥y"，主按钮是"支付并发布"。
没付成的任务留在"我的任务"里能接着付，超过 24 小时由后台关掉，不再变成
既看不见又删不掉的孤儿。

选宠物换成带头像的卡片，缺免疫记录或照片的当场标出来，不用等提交才知道。

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

im/backend/internal/app/pet_feed_pricing.go

@@ -0,0 +1,120 @@
+package app
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// A price the app fills in for you has to be defensible: a cat in a small city
+// is not a dog in Shenzhen. The table lives in config so operations can move it
+// without a release, and the number stays editable — the suggestion is a
+// starting point, not a rule.
+
+type priceSuggestConfig struct {
+	Base     map[string]int `json:"base"`      // 物种基准单价（分）
+	Cities   map[string]int `json:"cities"`    // 城市系数（百分比），键是城市编码前两位或全码
+	Minutes  map[string]int `json:"minutes"`   // 每次时长加价（分）
+	DogWalk  int            `json:"dogWalk"`   // 含遛狗时的额外加价（分）
+	Rounding int            `json:"rounding"`  // 取整到多少分
+}
+
+const defaultPriceSuggest = `{
+  "base": {"cat": 3000, "dog": 4500, "other": 3000},
+  "cities": {"11": 120, "31": 120, "44": 115, "51": 105, "33": 110},
+  "minutes": {"15": -300, "20": 0, "30": 500, "45": 1200},
+  "dogWalk": 500,
+  "rounding": 100
+}`
+
+func (a *App) priceSuggestConfig(ctx context.Context) priceSuggestConfig {
+	parsed := priceSuggestConfig{}
+	raw := strings.TrimSpace(a.configPlain(ctx, "pet.feed_price_suggest_json", ""))
+	if raw == "" || json.Unmarshal([]byte(raw), &parsed) != nil {
+		_ = json.Unmarshal([]byte(defaultPriceSuggest), &parsed)
+	}
+	if parsed.Rounding < 1 {
+		parsed.Rounding = 100
+	}
+	return parsed
+}
+
+// suggestFeedPrice returns the per-visit price in cents, plus the band the
+// server will accept, so the form can warn before the user submits.
+func (a *App) suggestFeedPrice(ctx context.Context, species, cityCode string, minutes int, walking bool) (int, int, int) {
+	config := a.priceSuggestConfig(ctx)
+	price, ok := config.Base[species]
+	if !ok {
+		price = config.Base["other"]
+	}
+	if price <= 0 {
+		price = 3000
+	}
+	// 先按城市系数缩放：同一件事在不同城市值不同的钱。
+	factor := 0
+	if code := strings.TrimSpace(cityCode); code != "" {
+		if value, hit := config.Cities[code]; hit {
+			factor = value
+		} else if len(code) >= 2 {
+			if value, hit = config.Cities[code[:2]]; hit {
+				factor = value
+			}
+		}
+	}
+	if factor <= 0 {
+		factor = 100
+	}
+	price = price * factor / 100
+	if extra, hit := config.Minutes[strconv.Itoa(minutes)]; hit {
+		price += extra
+	}
+	if walking {
+		price += config.DogWalk
+	}
+	minPrice := a.configInt(ctx, "pet.feed_min_price_cent", 2000)
+	maxPrice := a.configInt(ctx, "pet.feed_max_price_cent", 50000)
+	price = (price / config.Rounding) * config.Rounding
+	if price < minPrice {
+		price = minPrice
+	}
+	if price > maxPrice {
+		price = maxPrice
+	}
+	return price, minPrice, maxPrice
+}
+
+func (a *App) feedPriceSuggestion(w http.ResponseWriter, r *http.Request) {
+	query := r.URL.Query()
+	species := strings.TrimSpace(query.Get("species"))
+	if petID, err := strconv.ParseInt(strings.TrimSpace(query.Get("petId")), 10, 64); err == nil && petID > 0 {
+		var owned string
+		if a.db.QueryRowContext(r.Context(), `SELECT species FROM pets WHERE id=? AND owner_user_id=? AND deleted_at IS NULL`,
+			petID, current(r).ID).Scan(&owned) == nil {
+			species = owned
+		}
+	}
+	if _, ok := petSpecies[species]; !ok {
+		species = "other"
+	}
+	minutes, _ := strconv.Atoi(strings.TrimSpace(query.Get("minMinutes")))
+	if minutes <= 0 {
+		minutes = 20
+	}
+	cityCode := strings.TrimSpace(query.Get("cityCode"))
+	if cityCode == "" {
+		if addressID, err := strconv.ParseInt(strings.TrimSpace(query.Get("addressId")), 10, 64); err == nil && addressID > 0 {
+			_ = a.db.QueryRowContext(r.Context(), `SELECT city_code FROM pet_addresses WHERE id=? AND user_id=?`,
+				addressID, current(r).ID).Scan(&cityCode)
+		}
+	}
+	walking := strings.TrimSpace(query.Get("walk")) == "1" || species == "dog"
+
+	price, minPrice, maxPrice := a.suggestFeedPrice(r.Context(), species, cityCode, minutes, walking)
+	reply(w, map[string]any{
+		"priceCent": price, "minPriceCent": minPrice, "maxPriceCent": maxPrice,
+		"species": species, "cityCode": cityCode, "minMinutes": minutes,
+		"feePercent": a.configInt(r.Context(), "pet.feed_platform_fee_percent", 15),
+	})
+}