fix: always emit the mandatory C9 in the install parameters (v3.6.20)

The v3.6.17 prefix built `C9` only when its field was filled, so filling the
C7/C8 quotas with an empty C9 produced `EF…`-only Install Parameters - and
GP Table 11-49 makes C9 mandatory, so the card rejected the data field with
6A80 (decrypted live packet: params started `EF08C7020000C8020000EA25…`).

- `ramParamsPrefix` always emits the C9 TLV (empty -> `C900`, like the
  reference tools); the vendor form becomes `C900 EF08 C7020000 C8020000
  EA…`.
- the raw "Install parameters (hex)" field is relabelled "Extra install
  parameters (hex)" - it appends extra TLVs after the generated prefix.
- tests updated (empty prefix -> `C900`, quotas-only ->
  `C900EF08C7020000C8020000`).

650 frontend / 499 Python green; version 3.6.20; sw simple-v293.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pysim-simple-server"
-version = "3.6.19"
+version = "3.6.20"
 description = "HTTP REST server wrapping pysim for the SIMple PWA"
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.