fix(updater,install,docs): follow the move to FelisMC/Felis (#53)

The repository moved to FelisMC/Felis, but the felis-api release coordinate, the installer's default FELIS_REPO_URL, the PaperMC user-agent strings and both READMEs still named MliroLirrorsIngenuity/Felis. Live on the audit box, 'felis update' reported 'github: MliroLirrorsIngenuity/Felis releases/latest returned HTTP 404 -- ...', pointing operators at a coordinate that no longer exists; the old path keeps answering today only because GitHub still 301s the transfer (verified with a read token against api.github.com: old path 301, new path 200), and if that redirect is ever retired every install and every update check breaks with it.

Replace the coordinate in the six tracked files: the updater topology and both test fixtures, the bootstrap default URL and user-agent strings, and README.md/README_EN.md. Green live: the same command now reports 'github: FelisMC/Felis releases/latest returned HTTP 404 -- ...' (still 404 because the new home has published no stable release yet -- a release-process fact, not a code bug).

Gates: gofmt, go vet, go test ./..., deploy/bootstrap_test.sh all clean.

internal/updater/topology_test.go

@@ -11,7 +11,7 @@ import (
 // allowed to auto-apply.
 func TestTopologyEncodesPolicies(t *testing.T) {
 	want := map[string]Spec{
-		"felis-api":   {Name: "felis-api", Policy: updates.PolicyScheduled, Manageable: true, Source: sourceGitHub, Coord: "MliroLirrorsIngenuity/Felis"},
+		"felis-api":   {Name: "felis-api", Policy: updates.PolicyScheduled, Manageable: true, Source: sourceGitHub, Coord: "FelisMC/Felis"},
 		"k3s":         {Name: "k3s", Policy: updates.PolicyNotify, Manageable: false, Source: sourceGitHub, Coord: "k3s-io/k3s"},
 		"cloudflared": {Name: "cloudflared", Policy: updates.PolicyScheduled, Manageable: true, Source: sourceGitHub, Coord: "cloudflare/cloudflared"},
 		"velocity":    {Name: "velocity", Policy: updates.PolicyNotify, Manageable: false, Source: sourcePaperMC, Coord: "velocity"},