chore: rename gitea-projects-api → gitea-local-fork

The fork tracked by this derivation is no longer a single-feature
branch ("feat/projects-api") but the integration tip of Oleks's
local gitea fork ($HOME/projects/gitea, branch oleks/main), carrying
upstream/main + PR #37518 Projects REST API + a CI gate + fork-local
commits. Reflect the broader scope in the package and attribute name,
and document the local fork path + branch in the derivation header.

flake.nix

@@ -66,7 +66,7 @@
         # Native-only packages — skip on s390x cross (gitea's pnpm step and
         # cgo+sqlite link don't cross-compile cleanly).
         // nixpkgs.lib.optionalAttrs (sys == "x86_64-linux" || sys == "aarch64-linux") {
-          gitea-projects-api =
+          gitea-local-fork =
             let
               # Our fork's go.mod requires Go 1.26.3; nixpkgs at this pin has
               # only 1.26.0 (and unstable has 1.26.2). Bump the package's src.
@@ -78,7 +78,7 @@
                 };
               });
             in
-            pkgs.callPackage ./packages/gitea-projects-api.nix {
+            pkgs.callPackage ./packages/gitea-local-fork.nix {
               buildGoModule = pkgs.buildGoModule.override { inherit go; };
             };
         }