feat: set TG_UI_BASE_URL env var in TestGen compose file

[rboni-dk]

TestGen now requires deployments to declare their public URL. The installer auto-derives it from --port and --ssl-* flags and injects TG_UI_BASE_URL into the compose environment. The upgrade flow detects existing installs missing the variable and backfills it from the compose port mapping and SSL config.

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
dk-installer.py	1148	273	76%	98–99, 111–123, 143–144, 200, 240–247, 254, 266, 288–289, 331, 381–384, 403–404, 406, 456–485, 489–522, 553–562, 621, 757, 788–793, 867–868, 878, 894–898, 901, 904, 907, 918–951, 1072–1083, 1132–1147, 1150–1161, 1178–1179, 1216–1217, 1243–1244, 1251, 1256, 1262–1263, 1296–1299, 1308–1309, 1314–1315, 1331–1342, 1387–1389, 1568–1593, 1634–1637, 1707–1710, 1742, 1767–1769, 1823, 1825, 1827, 1938–1939, 1967, 2016–2055, 2095–2102, 2118–2126, 2199–2224, 2231–2240, 2249–2302, 2306–2341, 2345–2363
TOTAL	1148	273	76%

Tests	Skipped	Failures	Errors	Time
99	0 💤	0 ❌	0 🔥	1.300s ⏱️

[aarthy-dk]

Looks good!