feat: public platform, admin console, templates, landing docs

Projects become publicly browsable after admin approval; management and
secret-adjacent reads (logs, variables, exec, connection URLs) require
owner/member/admin auth, and platform controls sit behind RequireAdmin.

- Backend: OptionalAuth middleware, read/authed/admin route groups,
  projects.is_approved + service_templates.owner_id migration,
  visibility-aware sqlc queries, admin overview/users/approval endpoints,
  EnsureAdminAccount bootstrap (ADMIN_* env), 30 seeded templates with
  owner CRUD, managed-database connection URLs gated owner+admin, fix
  DB.Stats() infinite recursion.
- Frontend: expandable persisted sidebar + clickable user menu, public
  landing page with searchable docs browser (GitHub sync, bundled
  snapshot + localStorage fallback), DocsBrowser shared with /docs,
  template create/edit/JSON-upload for owned templates, database create
  dialog, admin console (stats, approvals, project edit/delete, user
  admin toggles), HA/Security/Usage polish with dead CSS tokens mapped
  to real theme vars, anonymous-safe gating on every mutation control.
- Tests: safe window.localStorage access fixes happy-dom crashes in
  PlatformShell and canvas storage.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/migrations_goose/20260924000000_public_platform.sql

@@ -0,0 +1,16 @@
+-- +goose Up
+-- Public platform model: projects are browsable without a session once the
+-- admin approves them; service_templates gains ownership for user templates.
+ALTER TABLE public.projects ADD COLUMN IF NOT EXISTS is_approved boolean NOT NULL DEFAULT false;
+
+-- Projects that already exist stay live; only newly created ones enter the
+-- approval queue.
+UPDATE public.projects SET is_approved = true;
+
+ALTER TABLE public.service_templates ADD COLUMN IF NOT EXISTS owner_id uuid;
+CREATE INDEX IF NOT EXISTS idx_service_templates_owner ON public.service_templates(owner_id);
+
+-- +goose Down
+ALTER TABLE public.projects DROP COLUMN IF EXISTS is_approved;
+DROP INDEX IF EXISTS public.idx_service_templates_owner;
+ALTER TABLE public.service_templates DROP COLUMN IF EXISTS owner_id;