refactor(backend): split stream routes into focused modules

Backend/routes/streams/schemas.ts

@@ -0,0 +1,29 @@
+import { z } from 'zod';
+
+export const requestStreamSchema = z.object({
+  cameraDeviceId: z.string().uuid(),
+  reason: z.enum(['on_demand', 'motion_follow_up']).default('on_demand'),
+  metadata: z.record(z.string(), z.unknown()).optional(),
+});
+
+export const acceptStreamSchema = z.object({
+  streamKey: z.string().trim().min(1).max(255).optional(),
+  metadata: z.record(z.string(), z.unknown()).optional(),
+});
+
+export const endStreamSchema = z.object({
+  reason: z.enum(['completed', 'cancelled', 'failed']).default('completed'),
+});
+
+export const streamParamSchema = z.object({
+  streamSessionId: z.string().uuid(),
+});
+
+export const sfuTransportRequestSchema = z.object({
+  role: z.enum(['camera', 'viewer']).optional(),
+});
+
+export const listSchema = z.object({
+  status: z.string().optional(),
+  limit: z.coerce.number().int().min(1).max(100).default(25),
+});