fix: robust author resolution for like/boost with URL pattern fallback

When lookupObject fails (Authorized Fetch, network issues) and the post
isn't in ap_timeline, likes returned 404 "Could not resolve post author".

Adds shared resolveAuthor() with 3 strategies:
1. lookupObject on post URL → getAttributedTo
2. Timeline + notifications DB lookup
3. Extract author from URL pattern (/users/NAME/, /@NAME/)

Refactors like, unlike, boost controllers to use the shared helper.

lib/controllers/interactions-boost.js

@@ -4,6 +4,7 @@
  */
 
 import { validateToken } from "../csrf.js";
+import { resolveAuthor } from "../resolve-author.js";
 
 /**
  * POST /admin/reader/boost — send an Announce activity to followers.
@@ -66,40 +67,38 @@ export function boostController(mountPath, plugin) {
         orderingKey: url,
       });
 
-      // Also send to the original post author (signed request for Authorized Fetch)
-      try {
-        const documentLoader = await ctx.getDocumentLoader({
-          identifier: handle,
-        });
-        const remoteObject = await ctx.lookupObject(new URL(url), {
-          documentLoader,
-        });
+      // Also send directly to the original post author
+      const documentLoader = await ctx.getDocumentLoader({
+        identifier: handle,
+      });
+      const { application } = request.app.locals;
+      const recipient = await resolveAuthor(
+        url,
+        ctx,
+        documentLoader,
+        application?.collections,
+      );
 
-        if (
-          remoteObject &&
-          typeof remoteObject.getAttributedTo === "function"
-        ) {
-          const author = await remoteObject.getAttributedTo({ documentLoader });
-          const recipient = Array.isArray(author) ? author[0] : author;
-
-          if (recipient) {
-            await ctx.sendActivity(
-              { identifier: handle },
-              recipient,
-              announce,
-              { orderingKey: url },
-            );
-          }
+      if (recipient) {
+        try {
+          await ctx.sendActivity(
+            { identifier: handle },
+            recipient,
+            announce,
+            { orderingKey: url },
+          );
+          console.info(
+            `[ActivityPub] Sent boost directly to ${recipient.id?.href || "author"}`,
+          );
+        } catch (error) {
+          console.warn(
+            `[ActivityPub] Direct boost delivery to author failed:`,
+            error.message,
+          );
         }
-      } catch (error) {
-        console.warn(
-          `[ActivityPub] lookupObject failed for ${url} (boost):`,
-          error.message,
-        );
       }
 
       // Track the interaction
-      const { application } = request.app.locals;
       const interactions = application?.collections?.get("ap_interactions");
 
       if (interactions) {