fix(stats): confirmed outranks worked in the band/mode matrix

Reported by VK4DX with the case that names itself: YB confirmed on 20m
digital, painted blue, because one unconfirmed YB station had also been
worked on that slot.

The ladder ran call_c > call_w > dxcc_c > dxcc_w, so a callsign worked and
not confirmed beat an entity CONFIRMED on the same band and mode. The grid
answers 'what do I still need here', and a confirmed entity needs nothing
whoever was worked afterwards — so the order is now call_c > dxcc_c >
call_w > dxcc_w.

Two things made it easy to get wrong, and both are fixed rather than
merely corrected. The code was a run of assignments where the later test
silently overwrote the earlier, so 'call worked' erased 'entity
confirmed'; it now takes the maximum. And the rule lived inside a scan
loop where nothing could reach it, so it is lifted into bandStatusCode
with a table test — including this exact case, and one that fails if
anybody reorders the constants.

internal/qso/qso.go

@@ -1895,7 +1895,8 @@ type WorkedBefore struct {
 
 	// Status grid driving the band×class matrix in the UI. One entry per
 	// (band, class) where ANY QSO exists in this DXCC. Only the highest
-	// status for that cell is kept (call_c > call_w > dxcc_c > dxcc_w).
+	// status for that cell is kept (call_c > dxcc_c > call_w > dxcc_w —
+	// confirmed outranks worked).
 	BandStatus []BandStatus `json:"band_status"`
 }
 
@@ -1906,6 +1907,48 @@ type BandStatus struct {
 	Status string `json:"status"` // "call_c" | "call_w" | "dxcc_c" | "dxcc_w"
 }
 
+// Band-status codes, lowest first. The ORDER is the rule: a cell shows the
+// highest that applies.
+const (
+	stDxccW = iota // the entity was worked on this slot
+	stCallW        // …and this callsign was one of them
+	stDxccC        // the entity is CONFIRMED here
+	stCallC        // …and by this callsign
+)
+
+// bandStatusNames maps those codes to what the UI colours by.
+var bandStatusNames = [...]string{"dxcc_w", "call_w", "dxcc_c", "call_c"}
+
+// bandStatusCode picks the status of one cell of the band × mode matrix.
+//
+// CONFIRMED OUTRANKS WORKED, and that is the whole of it. The ladder used to
+// run call_c > call_w > dxcc_c > dxcc_w, so a callsign worked and not confirmed
+// beat an entity confirmed on the same slot: an operator with YB confirmed on
+// 20m digital saw that cell as "worked, not confirmed" because he had also
+// worked one unconfirmed YB station there. The grid answers "what do I still
+// need", and a confirmed entity needs nothing, whoever was worked afterwards.
+//
+// Taken as a MAXIMUM rather than as a run of assignments, which is how the
+// later test came to overwrite the earlier one in the first place.
+func bandStatusCode(callWorked, callConfirmed, entityConfirmed bool) int {
+	code := stDxccW // there is a row at all ⇒ the entity was worked here
+	raise := func(c int) {
+		if c > code {
+			code = c
+		}
+	}
+	if callWorked {
+		raise(stCallW)
+	}
+	if entityConfirmed {
+		raise(stDxccC)
+	}
+	if callConfirmed {
+		raise(stCallC)
+	}
+	return code
+}
+
 // modeClass collapses ADIF modes into the three buckets DXers care about.
 // Anything not voice and not CW is treated as digital.
 func modeClass(mode string) string {
@@ -2167,7 +2210,18 @@ func (r *Repo) WorkedBefore(ctx context.Context, callsign string, dxccHint int,
 	// ---- Per-(band, class) status grid ----
 	// One pass over every distinct (band, mode) in the DXCC, aggregating
 	// "did this call work it?" and "was anything confirmed?" via MAX.
-	// Status precedence: call_c > call_w > dxcc_c > dxcc_w.
+	// Status precedence: CONFIRMED OUTRANKS WORKED — call_c > dxcc_c > call_w >
+	// dxcc_w.
+	//
+	// It used to run call_c > call_w > dxcc_c > dxcc_w, which made a call worked
+	// and not confirmed outrank an entity confirmed on the same slot. Reported
+	// from a real log: YB confirmed on 20m digital showed BLUE, because that
+	// operator had also worked one unconfirmed YB station there. The cell said
+	// "not confirmed" about a slot that is confirmed.
+	//
+	// The grid answers "what do I still need on this band and mode", and for
+	// that question confirmation is the axis that matters: a confirmed entity
+	// needs nothing, whoever else was worked afterwards.
 	// Filter NULL/empty band+mode rows — they'd create a NULL group key
 	// that Scan into *string can't handle and would error out the whole
 	// WorkedBefore call, blanking the matrix in the UI.
@@ -2188,12 +2242,6 @@ func (r *Repo) WorkedBefore(ctx context.Context, callsign string, dxccHint int,
 		return wb, fmt.Errorf("band status: %w", err)
 	}
 	type cellKey struct{ band, class string }
-	const (
-		stDxccW = 0
-		stDxccC = 1
-		stCallW = 2
-		stCallC = 3
-	)
 	best := map[cellKey]int{}
 	for statusRows.Next() {
 		var band, mode string
@@ -2202,23 +2250,14 @@ func (r *Repo) WorkedBefore(ctx context.Context, callsign string, dxccHint int,
 			statusRows.Close()
 			return wb, fmt.Errorf("scan band status: %w", err)
 		}
-		code := stDxccW // row exists ⇒ entity worked at minimum
-		if dxccConfirmed == 1 {
-			code = stDxccC
-		}
-		if callW == 1 {
-			code = stCallW
-		}
-		if callC == 1 {
-			code = stCallC
-		}
+		code := bandStatusCode(callW == 1, callC == 1, dxccConfirmed == 1)
 		k := cellKey{band: band, class: modeClass(mode)}
 		if cur, ok := best[k]; !ok || code > cur {
 			best[k] = code
 		}
 	}
 	statusRows.Close()
-	codeStr := [...]string{"dxcc_w", "dxcc_c", "call_w", "call_c"}
+	codeStr := bandStatusNames
 	for k, code := range best {
 		wb.BandStatus = append(wb.BandStatus, BandStatus{
 			Band: k.band, Class: k.class, Status: codeStr[code],