feat(shared): manual-session create/update contracts

Add CreateManualSessionInput and AdminUpdateSessionInput zod schemas plus
inferred types. packages/shared has no test runner, so these are exercised
via Task 2's API tests rather than a standalone parse test.

packages/shared/src/index.ts

@@ -86,3 +86,27 @@ export const AdminUser = z.object({
   created_at: z.string(),
 });
 export type AdminUser = z.infer<typeof AdminUser>;
+
+export const CreateManualSessionInput = z.object({
+  user_id: z.string(),
+  activity_id: z.number().int(),
+  insole_type: InsoleType,
+  pair_count: z.number().int().min(1),
+  start_time: z.string(),
+  end_time: z.string(),
+  paused_seconds: z.number().int().min(0).default(0),
+  notes: z.string().nullable().optional(),
+});
+export type CreateManualSessionInput = z.infer<typeof CreateManualSessionInput>;
+
+export const AdminUpdateSessionInput = z.object({
+  activity_id: z.number().int(),
+  insole_type: InsoleType.nullable(),
+  pair_count: z.number().int().min(1),
+  start_time: z.string(),
+  end_time: z.string().nullable(),
+  paused_seconds: z.number().int().min(0),
+  notes: z.string().nullable(),
+  status: SessionStatus,
+});
+export type AdminUpdateSessionInput = z.infer<typeof AdminUpdateSessionInput>;