feat(backend): state-change event detection + clone template on start

- PUT /timers/🆔 detect state→fired and state→completed transitions,
  emit timer.fired / timer.completed domain events
- PUT /routines/🆔 detect status→completed transition,
  emit routine.completed domain event
- POST /routines/:id/start (TODO-004): when isTemplate=true, clone the
  template into a new RoutineDoc instead of mutating in-place. Original
  template stays reusable. Non-templates still update in place.

All 6 ChronoMind event types are now fully wired end-to-end.

backend/src/modules/routines/routes.ts

@@ -10,6 +10,7 @@
  * POST   /routines/batch     — batch upsert
  */
 
+import crypto from 'node:crypto';
 import type { FastifyInstance } from 'fastify';
 import { BadRequestError, NotFoundError, ConflictError } from '@bytelyst/errors';
 import { extractAuth } from '../../lib/auth.js';
@@ -111,6 +112,9 @@ export async function routineRoutes(app: FastifyInstance) {
       throw new BadRequestError(parsed.error.issues.map(i => i.message).join('; '));
     }
 
+    // Snapshot old state for event detection
+    const oldRoutine = await repo.getRoutine(id, auth.sub);
+
     const { syncVersion, ...updates } = parsed.data;
     const result = await repo.updateRoutine(id, auth.sub, updates, syncVersion);
 
@@ -121,6 +125,11 @@ export async function routineRoutes(app: FastifyInstance) {
     }
     if (!result.doc) throw new NotFoundError('Routine not found');
 
+    // Emit domain event on completed transition
+    if (oldRoutine && result.doc.status === 'completed' && oldRoutine.status !== 'completed') {
+      getEventBus().emit('routine.completed', { routineId: id, userId: auth.sub, name: result.doc.name });
+    }
+
     req.log.info({ routineId: id, syncVersion }, 'Updated routine');
     return result.doc;
   });
@@ -155,15 +164,39 @@ export async function routineRoutes(app: FastifyInstance) {
     }
 
     const now = new Date().toISOString();
-    // TODO-004: Clone template instead of mutating in-place
-    // Priority: medium | Phase: A.1
-    // When routine.isTemplate is true:
-    //   1. Create a NEW RoutineDoc (crypto.randomUUID() for id) with isTemplate=false
-    //   2. Copy all fields from the template into the clone
-    //   3. Set the clone's status to 'active', startedAt to now, first step to 'active'
-    //   4. Leave the original template unchanged (status stays 'template')
-    //   5. Return the new clone, not the template
-    // This lets users reuse templates multiple times without losing the original.
+    const activeSteps = routine.steps.map((step, i) => ({
+      ...step,
+      status: i === 0 ? 'active' as const : 'pending' as const,
+      startedAt: i === 0 ? now : undefined,
+      completedAt: undefined,
+    }));
+
+    if (routine.isTemplate) {
+      // Clone template into a new routine — leave original unchanged
+      const cloneId = crypto.randomUUID();
+      const clone: RoutineDoc = {
+        ...routine,
+        id: cloneId,
+        isTemplate: false,
+        status: 'active',
+        currentStepIndex: 0,
+        startedAt: now,
+        elapsedBeforePause: 0,
+        steps: activeSteps,
+        createdAt: now,
+        lastSyncedAt: now,
+        syncVersion: 1,
+      };
+      delete clone._ts;
+      delete clone._etag;
+
+      const created = await repo.createRoutine(clone);
+      getEventBus().emit('routine.started', { routineId: cloneId, userId: auth.sub, name: routine.name });
+      req.log.info({ routineId: cloneId, templateId: id }, 'Started routine (cloned from template)');
+      return created;
+    }
+
+    // Non-template: update in place
     const result = await repo.updateRoutine(
       id,
       auth.sub,
@@ -171,11 +204,7 @@ export async function routineRoutes(app: FastifyInstance) {
         status: 'active' as const,
         currentStepIndex: 0,
         startedAt: now,
-        steps: routine.steps.map((step, i) => ({
-          ...step,
-          status: i === 0 ? 'active' as const : 'pending' as const,
-          startedAt: i === 0 ? now : undefined,
-        })),
+        steps: activeSteps,
       },
       routine.syncVersion
     );

backend/src/modules/timers/routes.ts

@@ -118,6 +118,9 @@ export async function timerRoutes(app: FastifyInstance) {
       throw new BadRequestError(parsed.error.issues.map(i => i.message).join('; '));
     }
 
+    // Snapshot old state for event detection
+    const oldTimer = await repo.getTimer(id, auth.sub);
+
     const { syncVersion, ...updates } = parsed.data;
     const result = await repo.updateTimer(id, auth.sub, updates, syncVersion);
 
@@ -128,6 +131,16 @@ export async function timerRoutes(app: FastifyInstance) {
     }
     if (!result.doc) throw new NotFoundError('Timer not found');
 
+    // Emit domain events on state transitions
+    if (oldTimer && result.doc.state !== oldTimer.state) {
+      const payload = { timerId: id, userId: auth.sub, label: result.doc.label };
+      if (result.doc.state === 'fired') {
+        getEventBus().emit('timer.fired', payload);
+      } else if (result.doc.state === 'completed') {
+        getEventBus().emit('timer.completed', payload);
+      }
+    }
+
     req.log.info({ timerId: id, syncVersion }, 'Updated timer');
     return result.doc;
   });