fix(categories): correct all 7 smart-folder bugs at source (PHASE 2) (#38)

frontend/src/api/client.js

@@ -94,13 +94,22 @@ function folderToRequest(slug, page, pageSize) {
     case 'starred':   return { ...base, isStarred: true };
     case 'sent':      return { ...base, gmailLabel: 'SENT' };
     case 'drafts':    return { ...base, gmailLabel: 'DRAFT' };
-    case 'archive':   return { ...base, isInInbox: false, isTrashed: false };
+    // Archive = filed away: not in inbox, not trashed, and NOT Sent/Spam/Draft/Chat.
+    // Excluding those labels stops sent mail leaking into Archive.
+    case 'archive':   return { ...base, isInInbox: false, isTrashed: false, excludeGmailLabels: ['SENT', 'DRAFT', 'SPAM', 'TRASH', 'CHAT'] };
     case 'spam':      return { ...base, gmailLabel: 'SPAM' };
     case 'trash':     return { ...base, isTrashed: true };
+    // Pinned = Gmail's "Important" marker (a real per-message flag), not "everything".
+    case 'pinned':    return { ...base, isImportant: true };
+    // Read Later = only emails the user explicitly flagged (local marker).
+    case 'readlater': return { ...base, isReadLater: true };
+    // Unlabelled = emails not filed under any user-created label.
+    case 'unlabelled': return { ...base, hasUserLabels: false };
     // ── Special filters ──
     case 'large':     return { ...base, minSizeBytes: 5_000_000 };
+    // Old Mail = strictly older than 6 months.
     case 'old': {
-      const d = new Date(); d.setFullYear(d.getFullYear() - 1);
+      const d = new Date(); d.setMonth(d.getMonth() - 6);
       return { ...base, to: d.toISOString().slice(0, 10) };
     }
     // ── Smart folders ──