style(project): format Go with gofmt, set up Prettier for the frontend

Run gofmt -w across the backend, normalising the manually-aligned := blocks
to the gofmt standard. No code behaviour changes.

Add Prettier (+ prettier-plugin-svelte) to the frontend with the SvelteKit
default config (tabs, single quotes) so formatting is reproducible, then run
it over the whole tree. Add format / format:check npm scripts and a
.prettierignore (build output, generated schema.ts, static assets).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/internal/service/category_service.go

@@ -10,14 +10,14 @@ import (
 	"tanabata/backend/internal/port"
 )
 
-const categoryObjectType          = "category"
-const categoryObjectTypeID int16  = 3 // third row in 007_seed_data.sql object_types
+const categoryObjectType = "category"
+const categoryObjectTypeID int16 = 3 // third row in 007_seed_data.sql object_types
 
 // CategoryParams holds the fields for creating or patching a category.
 type CategoryParams struct {
 	Name     string
 	Notes    *string
-	Color    *string         // nil = no change; pointer to empty string = clear
+	Color    *string // nil = no change; pointer to empty string = clear
 	Metadata json.RawMessage
 	IsPublic *bool
 }
@@ -176,4 +176,4 @@ func (s *CategoryService) Delete(ctx context.Context, id uuid.UUID) error {
 func (s *CategoryService) ListTags(ctx context.Context, categoryID uuid.UUID, params port.OffsetParams) (*domain.TagOffsetPage, error) {
 	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
 	return s.tags.ListByCategory(ctx, categoryID, params)
-}
+}

backend/internal/service/file_service.go

@@ -627,4 +627,4 @@ func extractEXIFWithDatetime(data []byte) (json.RawMessage, *time.Time) {
 		dt = &t
 	}
 	return json.RawMessage(b), dt
-}
+}

backend/internal/service/pool_service.go

@@ -10,7 +10,7 @@ import (
 	"tanabata/backend/internal/port"
 )
 
-const poolObjectType         = "pool"
+const poolObjectType = "pool"
 const poolObjectTypeID int16 = 4 // fourth row in 007_seed_data.sql object_types
 
 // PoolParams holds the fields for creating or patching a pool.
@@ -238,4 +238,4 @@ func (s *PoolService) Reorder(ctx context.Context, poolID uuid.UUID, fileIDs []u
 		return err
 	}
 	return s.pools.Reorder(ctx, poolID, fileIDs)
-}
+}

backend/internal/service/tag_service.go

@@ -10,15 +10,15 @@ import (
 	"tanabata/backend/internal/port"
 )
 
-const tagObjectType    = "tag"
-const tagObjectTypeID  int16 = 2 // second row in 007_seed_data.sql object_types
+const tagObjectType = "tag"
+const tagObjectTypeID int16 = 2 // second row in 007_seed_data.sql object_types
 
 // TagParams holds the fields for creating or patching a tag.
 type TagParams struct {
 	Name       string
 	Notes      *string
-	Color      *string          // nil = no change; pointer to empty string = clear
-	CategoryID *uuid.UUID       // nil = no change; Nil UUID = unassign
+	Color      *string    // nil = no change; pointer to empty string = clear
+	CategoryID *uuid.UUID // nil = no change; Nil UUID = unassign
 	Metadata   json.RawMessage
 	IsPublic   *bool
 }
@@ -422,4 +422,4 @@ func (s *TagService) expandTagSet(ctx context.Context, seeds []uuid.UUID) ([]uui
 	}
 
 	return queue, nil
-}
+}

backend/internal/service/user_service.go

@@ -189,4 +189,4 @@ func (s *UserService) Delete(ctx context.Context, id int16) error {
 	}
 	_ = s.audit.Log(ctx, "user_delete", nil, nil, map[string]any{"target_user_id": id})
 	return nil
-}
+}