fix(seasons): derive the FUT web-file base from openfut.cfg, not a lab IP

`STAGING_FUT_BASE` hardcoded `http://10.10.0.120:8110/fut/` into the hook
binary, so the base-supply rewriter only worked on one machine and could not be
merged.

The prefix now comes from the same `openfut.cfg` / `openfut-common` source of
truth as every redirect target: `fut_content_base()` builds
`http://<host>:<fut_content_port>/fut/` from the configured host.
`OpenFutPorts` gains `fut_content` with a named default
(`default_ports::FUT_CONTENT = 8110`) and an optional `fut_content_port=` key,
matching how every other OpenFUT port is already handled. A cfg written before
the key existed still parses and takes the default — failing it would disarm the
network redirect too.

Arming fails SAFE: an absent or unusable config arms nothing and the rewriter
leaves every url exactly as the client built it, rather than pointing it at a
guessed host. This also adds the `openfut-common` dependency to the hook on this
branch; main already has it.

Proof: the cross-built artifact no longer contains the string 10.10.0.120
(previously compiled in), openfut-common is green at 16 tests including the new
config-derived-base and backward-compatibility cases, and the launcher builds.

openfut-hook/Cargo.lock

@@ -2,10 +2,15 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "openfut-common"
+version = "0.1.0"
+
 [[package]]
 name = "openfut-hook"
 version = "0.1.0"
 dependencies = [
+ "openfut-common",
  "windows-sys",
 ]