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.

deploy/bootstrap.sh

@@ -84,7 +84,7 @@ set -Eeuo pipefail
 # ---------------------------------------------------------------------------
 # Configuration & constants
 # ---------------------------------------------------------------------------
-FELIS_REPO_URL="${FELIS_REPO_URL:-https://github.com/MliroLirrorsIngenuity/Felis.git}"
+FELIS_REPO_URL="${FELIS_REPO_URL:-https://github.com/FelisMC/Felis.git}"
 # Which version to install. "release" builds the newest published GitHub release;
 # "dev" builds the tip of main. Release is the default because an installer that
 # tracks a moving branch by default hands every new host a different, untested
@@ -1430,7 +1430,7 @@ resolve_game_jars() {
 luckperms_latest_jar() {
   local json url
   json="$(curl -fsSL --retry 5 --retry-delay 2 \
-    -A "felis-bootstrap (+https://github.com/MliroLirrorsIngenuity/Felis)" \
+    -A "felis-bootstrap (+https://github.com/FelisMC/Felis)" \
     "https://metadata.luckperms.net/data/all")" || return 1
   url="$(printf '%s' "$json" \
     | grep -o 'https://download\.luckperms\.net/[0-9]\{1,\}/bukkit/loader/[^"]*\.jar' || true)"
@@ -1452,7 +1452,7 @@ luckperms_latest_jar() {
 papermc_latest_jar() {
   local project="$1" version="$2" json urls url sha
   json="$(curl -fsSL --retry 5 --retry-delay 2 \
-    -A "felis-bootstrap (+https://github.com/MliroLirrorsIngenuity/Felis)" \
+    -A "felis-bootstrap (+https://github.com/FelisMC/Felis)" \
     "https://fill.papermc.io/v3/projects/${project}/versions/${version}/builds/latest")" || return 1
   urls="$(printf '%s' "$json" | grep -o 'https://fill-data\.papermc\.io/[^"]*\.jar' || true)"
   url="${urls%%$'\n'*}"