feat: cron job editor dialog (closes #150)

Implements a full-screen cron job editor dialog following the skills editor pattern:
- Create/edit/delete cron jobs with all backend fields
- CronJobRepeat data class matching backend object shape
- Fixed Gson crash on cron tab load

app/src/main/java/com/m57/hermescontrol/data/remote/HermesApiService.kt

@@ -3,6 +3,7 @@ package com.m57.hermescontrol.data.remote
 import com.m57.hermescontrol.data.model.AchievementsResponse
 import com.m57.hermescontrol.data.model.ActiveProfileResponse
 import com.m57.hermescontrol.data.model.AgentPluginInstallBody
+import com.m57.hermescontrol.data.model.CreateCronJobRequest
 import com.m57.hermescontrol.data.model.CreateTaskBody
 import com.m57.hermescontrol.data.model.CronJob
 import com.m57.hermescontrol.data.model.DoctorResponse
@@ -38,6 +39,7 @@ import com.m57.hermescontrol.data.model.SystemStatsResponse
 import com.m57.hermescontrol.data.model.ToggleSkillRequest
 import com.m57.hermescontrol.data.model.Toolset
 import com.m57.hermescontrol.data.model.ToolsetToggleRequest
+import com.m57.hermescontrol.data.model.UpdateCronJobRequest
 import com.m57.hermescontrol.data.model.UpdateProfileModelRequest
 import com.m57.hermescontrol.data.model.UpdateProfileSoulRequest
 import com.m57.hermescontrol.data.model.UpdateRawConfigRequest
@@ -103,6 +105,22 @@ interface HermesApiService {
         @Path("id") id: String,
     ): Response<Unit>
 
+    @GET("api/cron/jobs/{id}")
+    suspend fun getCronJob(
+        @Path("id") id: String,
+    ): Response<CronJob>
+
+    @POST("api/cron/jobs")
+    suspend fun createCronJob(
+        @Body body: CreateCronJobRequest,
+    ): Response<CronJob>
+
+    @PUT("api/cron/jobs/{id}")
+    suspend fun updateCronJob(
+        @Path("id") id: String,
+        @Body body: UpdateCronJobRequest,
+    ): Response<CronJob>
+
     @POST("api/cron/jobs/{id}/trigger")
     suspend fun triggerCronJob(
         @Path("id") id: String,