Phase 4: Architecture & tooling investment

Fixes a real N+1 API-call bug (per-cell project-member fetches in shot/asset
task-status cells, now a shared cached store), replaces a polling-based
in-flight request de-dup with promise memoization, adds markRaw() around
icon components in reactive state, and fixes a deep watcher that re-scanned
the whole projects array just to trigger thumbnail loading.

Introduces useAsyncAction and usePermission composables to cut duplicated
store boilerplate and duplicated role/admin checks, applied only where the
existing code was a clean match rather than forced onto everything. Extracts
assets.ts's shared per-asset optimistic-update/rollback helper without
merging the single and bulk API paths, which hit genuinely different
endpoints. Adds toast-on-error for previously-silent secondary loads and
fixes a dead try/catch in the router's auth-init guard along the way.

Also fixes a thumbnail-loading regression introduced earlier in this same
pass: the new ID-keyed watcher never fired on a repeat visit to the Projects
page when the store already held the same project list, so thumbnails
(local component state, reset per mount) silently stopped loading after the
first visit. Replaced the watcher with a direct call after each fetch.

Table virtualization, splitting the two largest view files, broad store
caching, and moving domain types into types/ were scoped out as separate,
higher-risk follow-ups (documented in frontend_tasks.md).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/stores/episodes.ts

@@ -1,6 +1,7 @@
 import { defineStore } from 'pinia'
 import { ref, computed } from 'vue'
 import { episodeService, type Episode, type EpisodeCreate, type EpisodeUpdate } from '@/services/episode'
+import { useAsyncAction } from '@/composables/useAsyncAction'
 
 export const useEpisodesStore = defineStore('episodes', () => {
   // State
@@ -8,6 +9,7 @@ export const useEpisodesStore = defineStore('episodes', () => {
   const currentEpisode = ref<Episode | null>(null)
   const isLoading = ref(false)
   const error = ref<string | null>(null)
+  const { run } = useAsyncAction({ isLoading, error })
 
   // Getters
   const getEpisodeById = computed(() => {
@@ -24,30 +26,17 @@ export const useEpisodesStore = defineStore('episodes', () => {
 
   // Actions
   const fetchEpisodes = async (projectId?: number) => {
-    try {
-      isLoading.value = true
-      error.value = null
-      
-      if (projectId) {
-        episodes.value = await episodeService.getProjectEpisodes(projectId)
-      } else {
-        episodes.value = await episodeService.getEpisodes()
-      }
-    } catch (err) {
-      error.value = err instanceof Error ? err.message : 'Failed to fetch episodes'
-      throw err
-    } finally {
-      isLoading.value = false
-    }
+    return run(async () => {
+      episodes.value = projectId
+        ? await episodeService.getProjectEpisodes(projectId)
+        : await episodeService.getEpisodes()
+    }, { errorMessage: 'Failed to fetch episodes' })
   }
 
   const fetchEpisode = async (episodeId: number) => {
-    try {
-      isLoading.value = true
-      error.value = null
-      
+    return run(async () => {
       const episode = await episodeService.getEpisode(episodeId)
-      
+
       // Update the episode in the list if it exists
       const index = episodes.value.findIndex(e => e.id === episodeId)
       if (index !== -1) {
@@ -55,81 +44,51 @@ export const useEpisodesStore = defineStore('episodes', () => {
       } else {
         episodes.value.push(episode)
       }
-      
+
       currentEpisode.value = episode
       return episode
-    } catch (err) {
-      error.value = err instanceof Error ? err.message : 'Failed to fetch episode'
-      throw err
-    } finally {
-      isLoading.value = false
-    }
+    }, { errorMessage: 'Failed to fetch episode' })
   }
 
   const createEpisode = async (projectId: number, episodeData: EpisodeCreate) => {
-    try {
-      isLoading.value = true
-      error.value = null
-      
+    return run(async () => {
       const newEpisode = await episodeService.createEpisode(projectId, episodeData)
       episodes.value.push(newEpisode)
-      
       return newEpisode
-    } catch (err) {
-      error.value = err instanceof Error ? err.message : 'Failed to create episode'
-      throw err
-    } finally {
-      isLoading.value = false
-    }
+    }, { errorMessage: 'Failed to create episode' })
   }
 
   const updateEpisode = async (episodeId: number, episodeData: EpisodeUpdate) => {
-    try {
-      isLoading.value = true
-      error.value = null
-      
+    return run(async () => {
       const updatedEpisode = await episodeService.updateEpisode(episodeId, episodeData)
-      
+
       // Update the episode in the list
       const index = episodes.value.findIndex(e => e.id === episodeId)
       if (index !== -1) {
         episodes.value[index] = updatedEpisode
       }
-      
+
       // Update current episode if it's the same
       if (currentEpisode.value?.id === episodeId) {
         currentEpisode.value = updatedEpisode
       }
-      
+
       return updatedEpisode
-    } catch (err) {
-      error.value = err instanceof Error ? err.message : 'Failed to update episode'
-      throw err
-    } finally {
-      isLoading.value = false
-    }
+    }, { errorMessage: 'Failed to update episode' })
   }
 
   const deleteEpisode = async (episodeId: number) => {
-    try {
-      isLoading.value = true
-      error.value = null
-      
+    return run(async () => {
       await episodeService.deleteEpisode(episodeId)
-      
+
       // Remove the episode from the list
       episodes.value = episodes.value.filter(e => e.id !== episodeId)
-      
+
       // Clear current episode if it's the deleted one
       if (currentEpisode.value?.id === episodeId) {
         currentEpisode.value = null
       }
-    } catch (err) {
-      error.value = err instanceof Error ? err.message : 'Failed to delete episode'
-      throw err
-    } finally {
-      isLoading.value = false
-    }
+    }, { errorMessage: 'Failed to delete episode' })
   }
 
   const setCurrentEpisode = (episode: Episode | null) => {