Add read endpoints for counter sales

The ingest only ever wrote. A bill that reached pos_orders was safe and
completely unreachable — no screen in the product could show it, and the
only way to see a day's counter takings was to query the database by
hand.

Three endpoints: a paged bill list, one bill with its lines, and a
summary split the three ways somebody actually asks for — by tender for
reconciling a drawer, by day for a chart, by till for an outlet running
several counters.

locationid is required on all of them and is the authorisation boundary,
so a caller cannot page through another shop's takings by omitting a
parameter. Fetching a bill under the wrong outlet returns 404 even when
the reference is a real one.

Dates match businessdate rather than arrival, because a till that was
offline overnight uploads yesterday's bills this morning and they belong
to yesterday. The list is ordered by billedat for the same reason —
sorting by arrival would interleave a recovered backlog through today.

Unlike the ingest handlers these answer in the usual envelope: they are
read by the web app, not by a terminal, and nothing about them is bound
to the till's contract.

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

controllers/posController.go

@@ -1,6 +1,7 @@
 package controllers
 
 import (
+	"fmt"
 	"log"
 	"net/http"
 	"strconv"
@@ -188,6 +189,107 @@ func (ctl *PosController) LocationHealth(c *fiber.Ctx) error {
 	})
 }
 
+// ---------------------------------------------------------------- Sales reads
+//
+// Unlike the ingest handlers above, these answer in the usual
+// `{code, message, status, details}` envelope — they are read by the web app,
+// not by a terminal, and nothing about them is bound to the till's contract.
+
+// posSalesFilter reads the shared query parameters.
+func posSalesFilter(c *fiber.Ctx) (models.PosSalesFilter, error) {
+	locationID, err := strconv.Atoi(strings.TrimSpace(c.Query("locationid")))
+	if err != nil || locationID <= 0 {
+		return models.PosSalesFilter{}, fmt.Errorf("locationid is required")
+	}
+
+	pageno, _ := strconv.Atoi(c.Query("pageno", "0"))
+	pagesize, _ := strconv.Atoi(c.Query("pagesize", "50"))
+
+	return models.PosSalesFilter{
+		Locationid:  locationID,
+		Fromdate:    strings.TrimSpace(c.Query("fromdate")),
+		Todate:      strings.TrimSpace(c.Query("todate")),
+		Terminalid:  strings.TrimSpace(c.Query("terminalid")),
+		Cashiername: strings.TrimSpace(c.Query("cashiername")),
+		Paymentmode: strings.TrimSpace(c.Query("paymentmode")),
+		Pageno:      pageno,
+		Pagesize:    pagesize,
+	}, nil
+}
+
+// GetSales lists counter bills for an outlet, newest first.
+func (ctl *PosController) GetSales(c *fiber.Ctx) error {
+	filter, err := posSalesFilter(c)
+	if err != nil {
+		return posBadRequest(c, err)
+	}
+
+	page, err := ctl.posService.Sales(filter)
+	if err != nil {
+		return posServerError(c, "GetSales", err)
+	}
+
+	return c.JSON(fiber.Map{"code": http.StatusOK, "status": true, "details": page})
+}
+
+// GetSaleDetail returns one bill with its lines.
+//
+// Accepts the terminal's order UUID, the invoice number, or this backend's
+// posorderid — a support call starts from whichever the caller is looking at.
+func (ctl *PosController) GetSaleDetail(c *fiber.Ctx) error {
+	locationID, err := strconv.Atoi(strings.TrimSpace(c.Query("locationid")))
+	if err != nil || locationID <= 0 {
+		return posBadRequest(c, fmt.Errorf("locationid is required"))
+	}
+
+	reference := strings.TrimSpace(c.Query("reference"))
+	if reference == "" {
+		return posBadRequest(c, fmt.Errorf("reference is required — an order id, invoice number or posorderid"))
+	}
+
+	bill, err := ctl.posService.SaleDetail(locationID, reference)
+	if err != nil {
+		return posServerError(c, "GetSaleDetail", err)
+	}
+	if bill == nil {
+		return c.Status(http.StatusNotFound).JSON(fiber.Map{
+			"code":    http.StatusNotFound,
+			"message": "no bill matches that reference at this outlet",
+			"status":  false,
+		})
+	}
+
+	return c.JSON(fiber.Map{"code": http.StatusOK, "status": true, "details": bill})
+}
+
+// GetSalesSummary totals a range, split by tender, day and till.
+func (ctl *PosController) GetSalesSummary(c *fiber.Ctx) error {
+	filter, err := posSalesFilter(c)
+	if err != nil {
+		return posBadRequest(c, err)
+	}
+
+	summary, err := ctl.posService.SalesSummary(filter)
+	if err != nil {
+		return posServerError(c, "GetSalesSummary", err)
+	}
+
+	return c.JSON(fiber.Map{"code": http.StatusOK, "status": true, "details": summary})
+}
+
+func posBadRequest(c *fiber.Ctx, err error) error {
+	return c.Status(http.StatusBadRequest).JSON(fiber.Map{
+		"code": http.StatusBadRequest, "message": err.Error(), "status": false,
+	})
+}
+
+func posServerError(c *fiber.Ctx, op string, err error) error {
+	log.Printf("pos %s: %v", op, err)
+	return c.Status(http.StatusInternalServerError).JSON(fiber.Map{
+		"code": http.StatusInternalServerError, "message": err.Error(), "status": false,
+	})
+}
+
 // posIngestError decides whether the terminal should retry.
 //
 // The distinction matters more than the message does. A misconfigured store id