Fix dropped change flags + FIDI parsing

- capture.py: DirectSniffer/GsmtapListener yield (type, data, flags),
  CaptureManager passes flags to insert_message (change flags were
  previously dropped, leaving every change row with flags=0)
- protocol.py: add _parse_fidi (1-byte value) — FIDI was mis-mapped to
  _parse_change (4-byte flags), so FIDI messages were silently dropped
- database.py: pass flags into decode_sniff_msg
- decode.py: decode_change(flags) reads flags directly; decode_sniff_msg
  gains flags parameter; change messages no longer require non-empty data
- tests: fix FIDI test, add change/fidi decode tests (43 total)

tests/test_decode.py

@@ -92,5 +92,32 @@ class TestCommandTypeTables(unittest.TestCase):
         self.assertEqual(ENVELOPE_TYPES[0xD6], 'EVENT DOWNLOAD')
 
 
+class TestChangeAndFidiDecoding(unittest.TestCase):
+    def test_change_reset_assert(self):
+        r = decode_sniff_msg(b'', 'change', flags=1 << 2)
+        self.assertEqual(r['type'], 'change')
+        self.assertEqual(r['flags'], ['Reset asserted'])
+
+    def test_change_card_insert(self):
+        r = decode_sniff_msg(b'', 'change', flags=1 << 0)
+        self.assertEqual(r['flags'], ['Card inserted'])
+
+    def test_change_multiple_flags(self):
+        r = decode_sniff_msg(b'', 'change', flags=(1 << 2) | (1 << 3))
+        self.assertEqual(r['flags'], ['Reset asserted', 'Reset de-asserted'])
+
+    def test_change_no_flags(self):
+        r = decode_sniff_msg(b'', 'change', flags=0)
+        self.assertEqual(r['flags'], ['no changes'])
+
+    def test_fidi(self):
+        r = decode_sniff_msg(b'\x97', 'fidi')
+        self.assertEqual(r['type'], 'fidi')
+        self.assertEqual(r['fi'], 9)
+        self.assertEqual(r['di'], 7)
+        self.assertEqual(r['fi_val'], 512)
+        self.assertEqual(r['di_val'], 64)
+
+
 if __name__ == '__main__':
     unittest.main()