fix(plugins): loader mod metadata — AGPL-3.0-only license, real issue tracker

The three loader mods declared `license = "MIT"` (and Forge/NeoForge a
placeholder `issueTrackerURL = https://example.invalid/felis`) while the
repository is AGPL-3.0-only (README.md:73, LICENSE).  The mods were added
2026-06-26, the LICENSE landed 2026-07-12 — stale leftovers that nothing
ever read back: no CI job, no install path.  Fabric loader prints the
license from fabric.mod.json at boot and both mods.toml files are parsed
by their loaders, so the wrong claim is user-visible.  Align both with
reality — boot-verified on real fabric/forge/neoforge dedicated servers
(AUDIT-2026-09-22.md, batch 41).

plugins/neoforge/src/main/resources/META-INF/mods.toml

@@ -1,7 +1,7 @@
 modLoader = "javafml"
 loaderVersion = "[1,)"
-license = "MIT"
-issueTrackerURL = "https://example.invalid/felis"
+license = "AGPL-3.0-only"
+issueTrackerURL = "https://github.com/FelisMC/Felis/issues"
 
 [[mods]]
 modId = "felis_link"