feat(ideas): add idea creator, grant calls and applications

Implement the idea creator and application generator: idea status workflow, social canvas card, grant call windows with 409 when closed, and an LLM-backed idea assistant with offline fallback.

backend/Infrastructure/Persistence/GrantCallService.cs

@@ -0,0 +1,65 @@
+using SurrealDb.Net;
+using TarninaHub.Application.Abstractions;
+using TarninaHub.Application.Dtos;
+
+namespace TarninaHub.Infrastructure.Persistence;
+
+public sealed class GrantCallService : IGrantCallService
+{
+    private const string SelectFields =
+        "type::string(id) AS id, name, opens_at, closes_at, status, external_id";
+
+    private readonly ISurrealDbClient _client;
+
+    public GrantCallService(ISurrealDbClient client)
+    {
+        _client = client;
+    }
+
+    public async Task<IReadOnlyList<GrantCallResponse>> ListAsync(
+        string? status,
+        CancellationToken cancellationToken)
+    {
+        var parameters = new Dictionary<string, object?>();
+        var where = string.Empty;
+
+        if (!string.IsNullOrWhiteSpace(status))
+        {
+            where = " WHERE status = $status";
+            parameters["status"] = status;
+        }
+
+        var response = await _client.RawQuery(
+            $"SELECT {SelectFields} FROM grant_call{where} ORDER BY opens_at DESC;",
+            parameters,
+            cancellationToken);
+        response.EnsureAllOks();
+
+        var rows = response.GetValue<List<GrantCallRow>>(0) ?? [];
+
+        return rows.Select(Map).ToList();
+    }
+
+    public async Task<GrantCallResponse?> GetAsync(string grantCallId, CancellationToken cancellationToken)
+    {
+        var (table, id) = SurrealRecordId.Split(grantCallId);
+
+        var response = await _client.RawQuery(
+            $"SELECT {SelectFields} FROM type::record($table, $id) LIMIT 1;",
+            new Dictionary<string, object?> { ["table"] = table, ["id"] = id },
+            cancellationToken);
+        response.EnsureAllOks();
+
+        var rows = response.GetValue<List<GrantCallRow>>(0) ?? [];
+
+        return rows.Count > 0 ? Map(rows[0]) : null;
+    }
+
+    private static GrantCallResponse Map(GrantCallRow row) => new(
+        row.Id,
+        row.Name,
+        row.OpensAt,
+        row.ClosesAt,
+        row.Status,
+        row.ExternalId);
+}