feat: V2 microservices stack — backend services, gateway, JWT auth

Add full V2 architecture: identity, content, studio (.NET 10) and file,
render, notification, gateway (Go) services with vendored deps, plus DB
migrations, event/API contracts, and an init-db script.

Wire the Next.js frontend to the gateway: server-side JWT auth routes
(login/register/refresh/logout/me), gateway fetch helper, and session/
cookie/jwt helpers under src/lib.

Containerize the stack via docker-compose.v2.yml and per-service
Dockerfiles. Base images resolve through a Nexus mirror (Docker Hub) and
MCR directly; npm/NuGet pull from Nexus groups. Self-host fonts via
next/font/local to avoid Google Fonts (geo-blocked).

Add CI workflow and ignore .env.v2, *.stackdump, and .NET bin/obj.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

services/studio/FlatRender.StudioSvc/Models/Responses/Responses.cs

@@ -0,0 +1,174 @@
+namespace FlatRender.StudioSvc.Models.Responses;
+
+public record PagedResponse<T>(IEnumerable<T> Items, PaginationMeta Meta);
+public record PaginationMeta(int Page, int PageSize, long Total, int TotalPages);
+public record ApiError(string Code, string Message, string? TraceId = null);
+
+public record SavedProjectSummaryResponse(
+    Guid Id,
+    Guid UserId,
+    Guid OriginalProjectId,
+    string OriginalProjectName,
+    string? OriginalContainerSlug,
+    string Name,
+    string? Image,
+    string Type,
+    string Resolution,
+    string ChooseMode,
+    decimal ProjectDurationSec,
+    DateTime LastEditDate,
+    DateTime CreatedAt
+);
+
+public record SavedProjectFullResponse(
+    Guid Id,
+    Guid UserId,
+    Guid OriginalProjectId,
+    string OriginalProjectName,
+    string? OriginalContainerSlug,
+    string Name,
+    string? Image,
+    string Type,
+    int FrameRate,
+    decimal ProjectDurationSec,
+    string Resolution,
+    string ChooseMode,
+    decimal VipFactor,
+    Guid? MusicFileId,
+    Guid? MusicTrackId,
+    decimal MusicVolume,
+    Guid? VoiceoverFileId,
+    decimal VoiceoverVolume,
+    bool VoiceoverRecordedInBrowser,
+    decimal SfxVolume,
+    bool SfxEnabled,
+    string? AudioVisualizerMusicUrl,
+    decimal? AudioVisualizerDurationSec,
+    bool ManualColorPicker,
+    Guid? SelectedPresetStoryId,
+    string? LastEditStep,
+    string EditState,
+    DateTime LastEditDate,
+    DateTime CreatedAt,
+    List<SavedSceneResponse> Scenes,
+    List<SavedSharedColorResponse> SharedColors,
+    List<SavedSharedColorPresetResponse> SharedColorPresets,
+    List<SavedSharedLayerResponse> SharedLayers
+);
+
+public record SavedSceneResponse(
+    long Id,
+    Guid? OriginalSceneId,
+    string Key,
+    string? Title,
+    string? Image,
+    string SceneType,
+    int Sort,
+    decimal SceneLengthSec,
+    decimal? MinDurationSec,
+    decimal? MaxDurationSec,
+    decimal OverlapAtEndSec,
+    bool CanHandleDuration,
+    bool ManualColorSelection,
+    long? SelectedColorPresetId,
+    List<SavedSceneContentResponse> Contents,
+    List<SavedSceneColorResponse> Colors,
+    List<SavedSceneColorPresetResponse> ColorPresets,
+    List<SavedSceneCharacterResponse> Characters
+);
+
+public record SavedSceneContentResponse(
+    long Id,
+    string Key,
+    string? Title,
+    string Type,
+    string? Value,
+    Guid? ValueFileId,
+    string? FileUrlCached,
+    string? FontFace,
+    int? FontSize,
+    string? Justify,
+    int PositionInContainer,
+    int DirectionLayerValue,
+    bool IsTextBox,
+    string? AiInputType,
+    int? SelectedDp,
+    string? RepeaterItemKey,
+    int? RepeaterIndex,
+    bool IsFocused,
+    string? MappedList,
+    int Sort
+);
+
+public record SavedSceneColorResponse(
+    long Id,
+    string ElementKey,
+    string? Title,
+    string? Icon,
+    string AttrValue,
+    string Value,
+    bool IsSelected,
+    int Sort
+);
+
+public record SavedSceneColorPresetResponse(
+    long Id,
+    bool IsSelected,
+    int Sort,
+    List<SavedColorPresetItemResponse> Items
+);
+
+public record SavedColorPresetItemResponse(long Id, string ElementKey, string Value, int Sort);
+
+public record SavedSceneCharacterResponse(
+    long Id,
+    Guid Key,
+    string? Name,
+    string? Icon,
+    List<SavedCharacterControllerResponse> Controllers
+);
+
+public record SavedCharacterControllerResponse(long Id, string? Name, string Key, string Value, int Sort);
+
+public record SavedSharedColorResponse(
+    long Id,
+    string ElementKey,
+    string? Title,
+    string? Icon,
+    string AttrValue,
+    string Value,
+    bool IsSelected,
+    int Sort
+);
+
+public record SavedSharedColorPresetResponse(
+    long Id,
+    string? Name,
+    bool IsSelected,
+    int Sort,
+    List<SavedColorPresetItemResponse> Items
+);
+
+public record SavedSharedLayerResponse(
+    long Id,
+    string Key,
+    string? Title,
+    string Type,
+    string? Value,
+    Guid? ValueFileId,
+    string? FileUrlCached,
+    string? FontFace,
+    int? FontSize,
+    string? Justify,
+    int PositionInContainer,
+    int DirectionLayerValue,
+    bool IsTextBox,
+    string? AiInputType,
+    string? MappedList,
+    int? Width,
+    int? Height,
+    bool IsFocused,
+    bool IsFontChangeable,
+    bool IsFontSizeChangeable,
+    int Sort
+);