fix(auth+pwa): resolve stuck-loading race condition and PWA build error

Auth: `getSession()` in a SvelteKit load function races with Supabase's async
localStorage init and can return null for a valid session, triggering a spurious
login() redirect. Moved auth redirect to (app)/+layout.svelte via $effect, which
correctly waits for onAuthStateChange to fire. Also fixed collective data never
loading on page refresh (INITIAL_SESSION event, not SIGNED_IN).

PWA: SvelteKit blocks Workbox imports in src/service-worker.ts, preventing
@vite-pwa/sveltekit from finding the compiled SW output. Switched to generateSW
strategy (plugin auto-generates the SW). Custom SW deferred to Fase 2b using
src/sw.ts (a filename SvelteKit does not intercept).

Docs: added gotchas 6–8 to CLAUDE.md covering both root causes so they are not
reintroduced. Updated plan/fase-2b with the sw.ts workaround note.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/lib/supabase.ts

@@ -10,7 +10,9 @@ export function getSupabase(): SupabaseClient<Database> {
 			auth: {
 				autoRefreshToken: true,
 				persistSession: true,
-				detectSessionInUrl: true,
+				// detectSessionInUrl is disabled: the /auth/callback page explicitly calls
+				// exchangeCodeForSession so there is only one code-exchange attempt.
+				detectSessionInUrl: false,
 				// PKCE flow — required for SPA/PWA OAuth
 				flowType: 'pkce'
 			}