revert: restore getMemoryStats as a query call

Sampling keeps to_candid calls bounded to ~10,000 per structure, so
query instruction limits are no longer a concern.

Made-with: Cursor

Author: rvanasa

backend/main/main-canister.mo

@@ -644,7 +644,7 @@ actor class Main() = this {
     sum * total / sampled;
   };
 
-  public shared ({ caller }) func getMemoryStats() : async MemoryStats {
+  public query ({ caller }) func getMemoryStats() : async MemoryStats {
     assert (Utils.isAdmin(caller));
 
     let dlStats = downloadLog.getMemoryStats();

cli/declarations/main/main.did

@@ -347,7 +347,7 @@ type Main =
           SemverPart;
         }) -> (Result_6) query;
    getHighestVersion: (name: PackageName) -> (Result_5) query;
-   getMemoryStats: () -> (MemoryStats);
+   getMemoryStats: () -> (MemoryStats) query;
    getMostDownloadedPackages: () -> (vec PackageSummary) query;
    getMostDownloadedPackagesIn7Days: () -> (vec PackageSummary) query;
    getNewPackages: () -> (vec PackageSummary) query;

cli/declarations/main/main.did.d.ts

@@ -111,7 +111,7 @@ export interface Main {
     Result_6
   >,
   'getHighestVersion' : ActorMethod<[PackageName], Result_5>,
-  'getMemoryStats' : ActorMethod<[], MemoryStats>,
+  'getMemoryStats' : ActorMethod<[], MemoryStats, 'query'>,
   'getMostDownloadedPackages' : ActorMethod<[], Array<PackageSummary>>,
   'getMostDownloadedPackagesIn7Days' : ActorMethod<[], Array<PackageSummary>>,
   'getNewPackages' : ActorMethod<[], Array<PackageSummary>>,

cli/declarations/main/main.did.js

@@ -342,7 +342,7 @@ export const idlFactory = ({ IDL }) => {
         ['query'],
       ),
     'getHighestVersion' : IDL.Func([PackageName], [Result_5], ['query']),
-    'getMemoryStats' : IDL.Func([], [MemoryStats], []),
+    'getMemoryStats' : IDL.Func([], [MemoryStats], ['query']),
     'getMostDownloadedPackages' : IDL.Func(
         [],
         [IDL.Vec(PackageSummary)],