proxy: use wherever http.Client is, update mautrix

Added a new common.ConfigurableTransport interface which mediabrowser,
ombi, jellyseer, discord, telegram and matrix (i.e.
ThirdPartService/ContactMethodLinker) now all implement. proxies are
bound to them in main.go, Email is still a special case (but from the
previous commit, mailgun does use the proxy).

mautrix/go has been updated, and context.TODO()s stuck everywhere since
I still don't really comprehend why I should use them (FIXME literally).

common/common.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"net/http"
 
 	lm "github.com/hrfee/jfa-go/logmessages"
 )
@@ -71,3 +72,8 @@ func GenericErr(status int, err error) error {
 		return ErrUnknown{code: status}
 	}
 }
+
+type ConfigurableTransport interface {
+	// SetTransport sets the http.Transport to use for requests. Can be used to set a proxy.
+	SetTransport(t *http.Transport)
+}

common/go.mod

@@ -4,4 +4,4 @@ replace github.com/hrfee/jfa-go/logmessages => ../logmessages
 
 go 1.22.4
 
-require github.com/hrfee/jfa-go/logmessages v0.0.0-20240805130902-86c37fb4237b
+require github.com/hrfee/jfa-go/logmessages v0.0.0-20240806200606-6308db495a0a