fix: keep the precise locator on digital QSOs; make the manual lookup real

Grid on the UDP path — WSJT-X and MSHV can only send a FOUR-character grid,
that is all the FT8 protocol carries. The enrichment rule there is "fill only
what is empty", so the coarse JN05 always won and QRZ's JN05JG was thrown away:
roughly 100 km of accuracy discarded on every digital QSO. The lookup grid is
now taken when it EXTENDS the received square. A lookup that disagrees outright
(JN18 against JN05) is not a refinement — the station may be portable and what
came over the air is then the better record. Both rules are pinned by tests.

Manual fetch in the QSO editor — it read the CACHE, valid for 30 days. An
operator who upgraded their QRZ subscription went on getting the thin
free-account record and clearing the cached row by hand was the only way out.
The button now forces a lookup that bypasses the cache, reaches the provider and
REFRESHES the stored row, with a 15 s budget instead of 2 s: a deliberate click
must reach the network, where giving up early would fall back to cty.dat and
look like nothing happened. The automatic type-ahead lookup keeps the cache,
which is where it earns its keep.

Same fetch: it used `??`, which only guards against null. Go marshals an unset
string as "", so a QRZ record with no grid BLANKED the grid already in the QSO.
The lookup still wins — that is the point of asking for it — but an empty
result no longer erases a good value.

app.go

@@ -6266,6 +6266,22 @@ func (a *App) SaveCabrilloFile() (string, error) {
 // Errors are returned as-is to the frontend; ErrNotFound surfaces as
 // "callsign not found".
 func (a *App) LookupCallsign(callsign string) (lookup.Result, error) {
+	return a.lookupCallsign(callsign, false)
+}
+
+// LookupCallsignFresh is the same, but SKIPS the cache and refreshes it.
+//
+// For a lookup the operator asked for by clicking, in the QSO editor. The cache
+// is right for the automatic lookup that fires while typing, but it also freezes
+// a wrong answer for its whole 30-day life: an operator who upgraded their QRZ
+// subscription went on getting the thin free-account record, and deleting the
+// cached row by hand was the only way out. A deliberate click must reach the
+// provider and overwrite what was stored.
+func (a *App) LookupCallsignFresh(callsign string) (lookup.Result, error) {
+	return a.lookupCallsign(callsign, true)
+}
+
+func (a *App) lookupCallsign(callsign string, force bool) (lookup.Result, error) {
 	if a.lookup == nil {
 		return lookup.Result{}, fmt.Errorf("lookup not initialized")
 	}
@@ -6287,6 +6303,16 @@ func (a *App) LookupCallsign(callsign string) (lookup.Result, error) {
 	}
 	ctx, cancel := context.WithTimeout(a.ctx, budget)
 	defer cancel()
+	if force {
+		// A forced lookup has to reach the network, so it gets a longer leash than
+		// the type-ahead one: giving up at 2 s would just fall back to cty.dat and
+		// look like the click did nothing.
+		cancel()
+		ctx, cancel = context.WithTimeout(a.ctx, 15*time.Second)
+		defer cancel()
+		ctx = lookup.WithForce(ctx)
+		applog.Printf("lookup: FORCED (cache bypassed) for %s", strings.ToUpper(strings.TrimSpace(callsign)))
+	}
 	r, err := a.lookup.Lookup(ctx, callsign)
 	if errors.Is(err, lookup.ErrNotFound) {
 		return lookup.Result{}, fmt.Errorf("callsign not found")
@@ -10290,6 +10316,31 @@ func (a *App) ReloadUDPIntegrations() []string {
 	return a.udp.Reload(a.ctx)
 }
 
+// refineGrid picks between the locator a QSO arrived with and the one the
+// callsign lookup returned.
+//
+// WSJT-X and MSHV always send a FOUR-character grid — that is all the FT8
+// protocol carries — so a QSO logged from them landed with JN05 while QRZ knew
+// JN05JG. The enrichment rule everywhere else on this path is "fill only what is
+// empty", which meant the coarse grid always won and the precise one was thrown
+// away, silently costing the operator ~100 km of accuracy on every digital QSO.
+//
+// The upgrade is only taken when the lookup grid EXTENDS the received one (same
+// first four characters). A lookup that disagrees outright — JN18 against JN05 —
+// is not a refinement: the station may be portable, and what came over the air
+// is then the better record. Case-insensitive, since ADIF grids arrive in both.
+func refineGrid(have, found string) string {
+	h := strings.ToUpper(strings.TrimSpace(have))
+	f := strings.ToUpper(strings.TrimSpace(found))
+	if h == "" {
+		return f
+	}
+	if len(f) > len(h) && strings.HasPrefix(f, h) {
+		return f
+	}
+	return h
+}
+
 // LogUDPLoggedADIF takes an ADIF blob received over UDP and inserts the
 // first record into the local logbook. Returns the ID of the inserted
 // row. Used by the auto-log handler (WSJT-X / JTDX / MSHV / JTAlert /
@@ -10357,9 +10408,7 @@ func (a *App) LogUDPLoggedADIF(adifText string) (int64, error) {
 			if q.Country == "" {
 				q.Country = lr.Country
 			}
-			if q.Grid == "" {
-				q.Grid = lr.Grid
-			}
+			q.Grid = refineGrid(q.Grid, lr.Grid)
 			if q.Continent == "" {
 				q.Continent = lr.Continent
 			}