Add 50/70 MHz band support (table, NOT-QRV, station setup, loggers)

Issue #68

Adds Band.B_50/B_70 and wires them through the same band-opportunity
machinery as the other bands: X/a/B+/o table columns and filter button
in the User table and the Workedstn database table, NOT-QRV checkboxes
and propagation across callsign variants, "My station uses 6m/4m band"
toggles, station-name detection ("50", "6M", "70MHZ", "4M" - without
stealing the existing bare "70"/"6" cm-band shorthand), Win-Test sked
band IDs (10/50MHz, 11/70MHz), and UCX-logger worked-band recognition.

Persists worked50/70 and notQRV50/70 via an additive SQLite migration
(same ensureColumnExists pattern as the earlier v1.1->v1.2 migration),
verified against a real database file.

ReachabilityService.resolveAutoBand() now also falls back to 50 MHz
(then 70 MHz) for stations in the "50/70 MHz" chat category, mirroring
the existing Microwave-category fallback to 23cm.

Assisted by Claude Sonnet 5 <noreply@anthropic.com>

src/main/java/kst4contest/controller/ReadUDPbyUCXMessageThread.java

@@ -144,6 +144,12 @@ public class ReadUDPbyUCXMessageThread extends Thread {
 		}
 
 		switch (band.trim()) {
+			case "50":
+			case "6m":
+				return Band.B_50;
+			case "70":
+			case "4m":
+				return Band.B_70;
 			case "144":
 			case "2m":
 				return Band.B_144;
@@ -357,6 +363,20 @@ public class ReadUDPbyUCXMessageThread extends Thread {
 						Band workedBand = helper_resolveBandFromLoggerBand(band);
 
 						switch (band) {
+						case "50":
+						case "6m":
+						{
+							workedCall.setWorked50(true);
+							break;
+						}
+
+						case "70":
+						case "4m":
+						{
+							workedCall.setWorked70(true);
+							break;
+						}
+
 						case "144":
 						case "2m": //minos contest logger
 						{
@@ -434,7 +454,13 @@ public class ReadUDPbyUCXMessageThread extends Thread {
 
 									modifyThat.setWorked(true);
 
-									if (workedCall.isWorked144()) {
+									if (workedCall.isWorked50()) {
+										modifyThat.setWorked50(true);
+
+									} else if (workedCall.isWorked70()) {
+										modifyThat.setWorked70(true);
+
+									} else if (workedCall.isWorked144()) {
 										modifyThat.setWorked144(true);
 
 									} else if (workedCall.isWorked432()) {