Remove inter-session waiting period for immediate sequential access

- Set SESSION_UNLOCK_INTERVAL_MS to 0 in backend and frontend.
- Allow immediate access to next eligible session upon completing previous sessions.
- Preserve all session prerequisites, assignment unlock logic, and participant progress.
- Update tests to verify immediate session unlock and assignment availability.

src/lib/sessionUnlock.ts

@@ -1,7 +1,7 @@
 import { PROGRAM_SESSION_COUNT } from '@/data/program/sessions';
 
-/** Minimum wait after completing session N before session N+1 unlocks (sessions 3–10). */
-export const SESSION_UNLOCK_INTERVAL_MS = 24 * 60 * 60 * 1000;
+/** Minimum wait after completing session N before session N+1 unlocks. Set to 0 so next session unlocks immediately. */
+export const SESSION_UNLOCK_INTERVAL_MS = 0;
 
 export type SessionCompletionTimes = Record<number, string>;
 

src/services/programService.ts

@@ -334,8 +334,7 @@ export async function submitHomeworkReport(
 
 /**
  * Check if a specific session is unlocked for a user.
- * Session N unlocks when sessions 1…N-1 are complete and at least 1 hour has passed
- * since session N-1 was completed.
+ * Session N unlocks immediately when previous sessions 1…N-1 are complete.
  */
 export function isSessionUnlocked(userId: string, sessionOrder: number): boolean {
   const cachedSessions = getSessions(userId);