feat: tags.pub global hashtag discovery integration (v3.8.0)

- Add setGlobalFollow/removeGlobalFollow/getFollowedTagsWithState to
  followed-tags storage; unfollowTag now preserves global follow state
- Add followTagGloballyController/unfollowTagGloballyController that
  send AP Follow/Undo via Fedify to tags.pub actor URLs
- Register POST /admin/reader/follow-tag-global and unfollow-tag-global
  routes with plugin reference for Fedify access
- Tag timeline controller passes isGloballyFollowed + error query param
- Tag timeline template adds global follow/unfollow buttons with globe
  indicator and inline error display
- Wire GET /api/v1/followed_tags to return real data with globalFollow state
- Add i18n keys: followGlobally, unfollowGlobally, globallyFollowing,
  globalFollowError

lib/mastodon/routes/stubs.js

@@ -21,6 +21,7 @@
 import express from "express";
 import { serializeStatus } from "../entities/status.js";
 import { parseLimit, buildPaginationQuery, setPaginationHeaders } from "../helpers/pagination.js";
+import { getFollowedTagsWithState } from "../../storage/followed-tags.js";
 
 const router = express.Router(); // eslint-disable-line new-cap
 
@@ -276,8 +277,29 @@ router.get("/api/v1/featured_tags", (req, res) => {
 
 // ─── Followed tags ──────────────────────────────────────────────────────────
 
-router.get("/api/v1/followed_tags", (req, res) => {
-  res.json([]);
+router.get("/api/v1/followed_tags", async (req, res, next) => {
+  try {
+    const collections = req.app.locals.mastodonCollections;
+    if (!collections?.ap_followed_tags) {
+      return res.json([]);
+    }
+
+    const pluginOptions = req.app.locals.mastodonPluginOptions || {};
+    const publicationUrl = pluginOptions.publicationUrl || "";
+    const tags = await getFollowedTagsWithState({ ap_followed_tags: collections.ap_followed_tags });
+
+    const response = tags.map((doc) => ({
+      id: doc._id.toString(),
+      name: doc.tag,
+      url: `${publicationUrl.replace(/\/$/, "")}/tags/${doc.tag}`,
+      history: [],
+      following: true,
+    }));
+
+    res.json(response);
+  } catch (error) {
+    next(error);
+  }
 });
 
 // ─── Suggestions ────────────────────────────────────────────────────────────