feat(tier2): event branding + UX polish — Block D

Backend
- Migration 0010 adds event_branding (one row per event; all fields
  nullable so a brand-new event renders with defaults)
- BrandingRepo with COALESCE/NULLIF upsert semantics: nil pointer
  preserves the existing value, "" clears the field to NULL
- internal/uploads package: ImageStore interface + LocalFSStore (dev),
  pure-stdlib decode + re-encode that strips EXIF and rejects anything
  that isn't valid JPEG/PNG. Size cap 2 MB, random 16-byte filenames
- GET /events/{id}/branding (viewer+) returns the row plus the
  AllowedFonts list so the frontend picker stays in sync
- PUT /events/{id}/branding (editor+) validates hex colours, font
  allowlist, and refuses image URLs whose path doesn't start with
  /uploads/ (blocks arbitrary-origin <img> smuggling on guest pages)
- POST /uploads/image (authed) → fresh CDN URL; GET /uploads/{file}
  serves with year-long cache (immutable random names)
- GET /access/{token} now embeds the host's branding so the RSVP page
  can render in their colours/font with their logo + cover
- docker-compose mounts a named volume for uploads
- Custom-domain sub-block deferred to Tier 3 per the plan

Frontend
- BrandingCard.vue: colour pickers, font dropdown, logo + cover upload
  with progressive disclosure, live preview pane that re-renders on
  every keystroke
- RSVP page applies branding via CSS vars at the section root, so
  primary colour theme + font cascade through every child card. Cover
  image renders as a banner above the form; logo lands in the header
- Submit button background switches to var(--brand-primary) when set
- Mounted on the event detail page below the guests block

Plus the small UX fixes from the e2e walkthrough:
- Nav: dropped the top-level "Events" link; the logo doubles as the
  home affordance (→ /dashboard when signed in, → / otherwise). Account
  + Billing + Sign out live under a profile dropdown (avatar with
  initials, opens on click, closes on outside-click / Esc / route nav)
- Renamed "Back to dashboard" → "Back to events" across event detail,
  billing, account, and new-event pages

Tests
- TestBrandingGetReturnsDefaults / TestBrandingPutPersists /
  TestBrandingPutRejectsBadInputs / TestUploadAndServeImage /
  TestUploadRejectsNonImage — all pass
- Domain tests for IsValidHexColor + IsAllowedFont
- Full integration suite green (176s)

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

test/integration/csv_import_test.go

@@ -11,6 +11,7 @@ import (
 	"mime/multipart"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 	"time"
 
@@ -142,6 +143,10 @@ func setupAuthedAPI(t *testing.T, ctx context.Context) (srv *httptest.Server, db
 	t.Cleanup(db.Close)
 	must(t, db.Migrate(ctx), "migrate")
 
+	// Block D — branding test pulls GG_UPLOADS_DIR from env to control
+	// the on-disk location of uploaded images. Other tests don't care,
+	// so an empty value (the default) leaves uploads disabled (POST
+	// /uploads/image returns 503) and the rest of the server still works.
 	apiSrv, err := api.NewServer(api.ServerDeps{
 		Logger:               logger,
 		DB:                   db,
@@ -153,6 +158,8 @@ func setupAuthedAPI(t *testing.T, ctx context.Context) (srv *httptest.Server, db
 		EmailVerificationTTL: 1 * time.Hour,
 		PasswordResetTTL:     1 * time.Hour,
 		PublicBaseURL:        "http://localhost",
+		UploadsDir:           os.Getenv("GG_UPLOADS_DIR"),
+		UploadsPublicURL:     os.Getenv("GG_UPLOADS_PUBLIC_URL"),
 	})
 	must(t, err, "build api server")
 	srv = httptest.NewServer(apiSrv.Handler())