refactor: migrate CRM data layer from manual gqlFetch to Apollo Client

Replace custom gqlFetch() with proper Apollo useQuery/useMutation hooks
powered by codegen-generated TypedDocumentNode types. Key changes:

- Add GraphQL SDL schema file and codegen config for typescript-vue-apollo
- Replace all 28 raw .graphql imports with generated typed documents
- Add 12 useQuery() hooks with cache-and-network fetch policy
- Add 17 useMutation() hooks with surgical refetchQueries per mutation
- Optimistic cache update for setContactInboxHidden (instant archive UX)
- Fix contact list subtitle: show lastText instead of channel name
- Migrate login page from gqlFetch to useMutation
- WebSocket realtime now calls Apollo refetch instead of full data reload

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

frontend/codegen.ts

@@ -1,16 +1,13 @@
 import type { CodegenConfig } from "@graphql-codegen/cli";
 
-const schemaUrl = process.env.GRAPHQL_SCHEMA_URL || process.env.GRAPHQL_HTTP_ENDPOINT || "http://localhost:3000/api/graphql";
-
 const config: CodegenConfig = {
-  schema: schemaUrl,
+  schema: "graphql/schema.graphql",
   documents: ["graphql/operations/**/*.graphql"],
   generates: {
-    "composables/graphql/generated.ts": {
+    "graphql/generated.ts": {
       plugins: [
         "typescript",
         "typescript-operations",
-        "typed-document-node",
         "typescript-vue-apollo",
       ],
       config: {
@@ -18,6 +15,7 @@ const config: CodegenConfig = {
         vueCompositionApiImportFrom: "vue",
         dedupeFragments: true,
         namingConvention: "keep",
+        useTypeImports: true,
       },
     },
   },