feat: Labels-Feature vollständig entfernen (PROJ-9)

Backend:
- internal/labelstore/ gelöscht (Store, Schema, CRUD)
- internal/api/label_handlers.go gelöscht (alle Label-Routen)
- internal/api/server.go: labels-Feld + SetLabels() entfernt
- internal/api/search_handlers.go: label_id-Filter + Enrichment entfernt
- internal/index/index.go: LabelID aus SearchRequest entfernt
- internal/imapserver/server.go: labels-Feld + labelbasierte Mailboxen entfernt
- cmd/archivmail/main.go: labelstore-Init + SetLabels() entfernt
- cmd/archivmail/version.go: labelstore-Modul entfernt, index-Kommentar korrigiert

Frontend:
- LabelList.tsx, LabelPicker.tsx, LabelsTab.tsx gelöscht
- src/lib/api/system.ts: MailLabel/LabelRule-Typen + alle Label-Funktionen entfernt
- src/lib/api/index.ts: Label-Exports entfernt
- src/app/search/page.tsx: LabelList + selectedLabelId State entfernt
- src/app/mail/[id]/page.tsx: LabelPicker + Labels-State entfernt
- src/app/admin/page.tsx: LabelsTab + alle Label-Handler/State entfernt

Docs:
- features/PROJ-9: Status auf Removed gesetzt
- features/INDEX.md: PROJ-9 auf Removed gesetzt

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

src/app/search/page.tsx

@@ -5,7 +5,6 @@ import { useRouter } from "next/navigation";
 import { useAuth } from "@/hooks/useAuth";
 import { searchEmails, exportMailsZIP, uploadMailFilesUser, getUploadProgressUser, type SearchHit, type UploadJob } from "@/lib/api";
 import { Navbar } from "@/components/navbar";
-import { LabelList } from "@/components/LabelList";
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Card, CardContent } from "@/components/ui/card";
@@ -57,7 +56,6 @@ export default function SearchPage() {
   const [dateTo, setDateTo] = useState("");
   const [sort, setSort] = useState("date_desc");
   const [hasAttachment, setHasAttachment] = useState<boolean | undefined>(undefined);
-  const [selectedLabelId, setSelectedLabelId] = useState<number | null>(null);
 
   const [results, setResults] = useState<SearchHit[]>([]);
   const [total, setTotal] = useState(0);
@@ -96,7 +94,6 @@ export default function SearchPage() {
           date_to: dateTo || undefined,
           sort: sort !== "date_desc" ? sort : undefined,
           has_attachment: hasAttachment,
-          label_id: selectedLabelId ?? undefined,
           page: p,
           page_size: PAGE_SIZE,
         });
@@ -111,7 +108,7 @@ export default function SearchPage() {
         setSearching(false);
       }
     },
-    [query, fromFilter, toFilter, dateFrom, dateTo, sort, hasAttachment, selectedLabelId]
+    [query, fromFilter, toFilter, dateFrom, dateTo, sort, hasAttachment]
   );
 
   // Superadmin has no mail access — redirect to admin dashboard
@@ -139,13 +136,6 @@ export default function SearchPage() {
       .finally(() => setSearching(false));
   }, [user]);
 
-  // Re-search when label selection changes
-  useEffect(() => {
-    if (!user || !searched) return;
-    doSearch(1);
-    // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [selectedLabelId]);
-
   function handleSubmit(e: React.FormEvent) {
     e.preventDefault();
     doSearch(1);
@@ -234,16 +224,6 @@ export default function SearchPage() {
         )}
         {!authLoading && user && (<>
         <div className="flex gap-6">
-        {/* Label sidebar — nur für Rollen mit eigenen Mails */}
-        {user.role !== "auditor" && user.role !== "domain_auditor" && (
-        <div className="hidden md:block w-48 shrink-0">
-          <LabelList
-            selectedLabelId={selectedLabelId}
-            onLabelSelect={setSelectedLabelId}
-          />
-        </div>
-        )}
-
         {/* Main content */}
         <div className="flex-1 min-w-0">
         <form onSubmit={handleSubmit} className="space-y-4">