refactor: split admin.ts into sub-modules (P2-11)

Extracts 3833-line admin.ts into focused modules:
- src/routes/admin/ui.ts       — layout() and clampText() helpers
- src/routes/admin/helpers.ts  — KV list helpers (listAllFeeds, addFeedToList, etc.)
- src/routes/admin/feeds.ts    — feed CRUD routes (feedsRouter)
- src/routes/admin/emails.ts   — email view/delete routes (emailsRouter)

admin.ts now mounts the sub-routers and retains only auth middleware,
dashboard, login/logout, and the in-place feed API update route.
All 163 tests continue to pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/admin/helpers.ts

@@ -0,0 +1,130 @@
+import { FeedList, FeedListItem } from "../../types";
+import { FEEDS_LIST_KEY } from "../../config/constants";
+import { logger } from "../../lib/logger";
+
+export async function deleteKeysWithConcurrency(
+  emailStorage: KVNamespace,
+  keys: string[],
+  concurrency: number,
+): Promise<{ ok: string[]; failed: string[] }> {
+  const uniqueKeys = Array.from(new Set(keys.filter(Boolean)));
+  const ok: string[] = [];
+  const failed: string[] = [];
+  const limit = Math.max(1, Math.floor(concurrency) || 1);
+
+  for (let i = 0; i < uniqueKeys.length; i += limit) {
+    const batch = uniqueKeys.slice(i, i + limit);
+    const results = await Promise.allSettled(
+      batch.map((key) => emailStorage.delete(key)),
+    );
+    results.forEach((result, idx) => {
+      const key = batch[idx];
+      if (result.status === "fulfilled") {
+        ok.push(key);
+      } else {
+        failed.push(key);
+      }
+    });
+  }
+
+  return { ok, failed };
+}
+
+export async function listAllFeeds(
+  emailStorage: KVNamespace,
+): Promise<FeedListItem[]> {
+  try {
+    const feedList = (await emailStorage.get(FEEDS_LIST_KEY, {
+      type: "json",
+    })) as FeedList | null;
+    return feedList?.feeds || [];
+  } catch (error) {
+    logger.error("Error listing feeds", { error: String(error) });
+    return [];
+  }
+}
+
+export async function addFeedToList(
+  emailStorage: KVNamespace,
+  feedId: string,
+  title: string,
+  description?: string,
+): Promise<void> {
+  try {
+    const feedList = ((await emailStorage.get(FEEDS_LIST_KEY, {
+      type: "json",
+    })) as FeedList | null) || { feeds: [] };
+
+    feedList.feeds.push({ id: feedId, title, description });
+    await emailStorage.put(FEEDS_LIST_KEY, JSON.stringify(feedList));
+  } catch (error) {
+    logger.error("Error adding feed to list", { feedId, error: String(error) });
+  }
+}
+
+export async function updateFeedInList(
+  emailStorage: KVNamespace,
+  feedId: string,
+  title: string,
+  description?: string,
+): Promise<void> {
+  try {
+    const feedList = ((await emailStorage.get(FEEDS_LIST_KEY, {
+      type: "json",
+    })) as FeedList | null) || { feeds: [] };
+
+    const feedIndex = feedList.feeds.findIndex((feed) => feed.id === feedId);
+    if (feedIndex !== -1) {
+      feedList.feeds[feedIndex].title = title;
+      feedList.feeds[feedIndex].description = description;
+      await emailStorage.put(FEEDS_LIST_KEY, JSON.stringify(feedList));
+    }
+  } catch (error) {
+    logger.error("Error updating feed in list", {
+      feedId,
+      error: String(error),
+    });
+  }
+}
+
+export async function removeFeedsFromListBulk(
+  emailStorage: KVNamespace,
+  feedIds: string[],
+): Promise<string[]> {
+  try {
+    const feedList = ((await emailStorage.get(FEEDS_LIST_KEY, {
+      type: "json",
+    })) as FeedList | null) || { feeds: [] };
+
+    const toRemove = new Set(feedIds.filter(Boolean));
+    if (toRemove.size === 0) return [];
+
+    const removed: string[] = [];
+    const nextFeeds: FeedListItem[] = [];
+
+    for (const feed of feedList.feeds) {
+      if (toRemove.has(feed.id)) {
+        removed.push(feed.id);
+        continue;
+      }
+      nextFeeds.push(feed);
+    }
+
+    if (removed.length === 0) return [];
+
+    feedList.feeds = nextFeeds;
+    await emailStorage.put(FEEDS_LIST_KEY, JSON.stringify(feedList));
+    return removed;
+  } catch (error) {
+    logger.error("Error removing feeds from list", { error: String(error) });
+    return [];
+  }
+}
+
+export async function removeFeedFromList(
+  emailStorage: KVNamespace,
+  feedId: string,
+): Promise<boolean> {
+  const removed = await removeFeedsFromListBulk(emailStorage, [feedId]);
+  return removed.includes(feedId);
+}