feat(navigation) : preserve list state in URL and use browser history for back buttons

Add useUrlState composable to sync page, search, sort and filter state
with URL query params. Back/forward navigation now restores the exact
list position. Replace hardcoded NuxtLink back buttons with
router.back() across all create/edit pages. Fix documents attachment
filter that checked non-existent ID fields instead of relation objects.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/composables/useUrlState.ts

@@ -0,0 +1,116 @@
+import { ref, watch, nextTick, type Ref } from 'vue'
+import { useRoute, useRouter } from '#imports'
+
+interface ParamDef<T extends string | number = string | number> {
+  default: T
+  type?: 'string' | 'number'
+  /** Debounce URL writes (ms). Default: 0 (immediate). */
+  debounce?: number
+}
+
+type ParamDefs = Record<string, ParamDef>
+
+type InferRef<D extends ParamDef> = D['default'] extends number ? Ref<number> : Ref<string>
+
+type StateRefs<T extends ParamDefs> = {
+  [K in keyof T]: InferRef<T[K]>
+}
+
+interface UseUrlStateOptions {
+  /** Called when state is restored from URL (back/forward navigation). */
+  onRestore?: () => void
+}
+
+export function useUrlState<T extends ParamDefs>(
+  params: T,
+  options?: UseUrlStateOptions,
+): StateRefs<T> {
+  const route = useRoute()
+  const router = useRouter()
+
+  const keys = Object.keys(params) as (keyof T & string)[]
+  const refs: Record<string, Ref<string | number>> = {}
+  const timers: Record<string, ReturnType<typeof setTimeout> | null> = {}
+
+  for (const key of keys) {
+    refs[key] = ref(parseValue(route.query[key], params[key]!))
+    timers[key] = null
+  }
+
+  let isProgrammatic = false
+
+  const buildQuery = (): Record<string, string> => {
+    const q: Record<string, string> = {}
+    for (const key of keys) {
+      const val = refs[key]!.value
+      if (val !== params[key]!.default) {
+        q[key] = String(val)
+      }
+    }
+    return q
+  }
+
+  const pushToUrl = () => {
+    if (isProgrammatic) return
+    isProgrammatic = true
+    const query = buildQuery()
+    router
+      .replace({ path: route.path, query })
+      .catch(() => {})
+      .finally(() => {
+        nextTick(() => {
+          isProgrammatic = false
+        })
+      })
+  }
+
+  for (const key of keys) {
+    const ms = params[key]!.debounce ?? 0
+    watch(refs[key]!, () => {
+      if (isProgrammatic) return
+      if (ms > 0) {
+        if (timers[key]) clearTimeout(timers[key]!)
+        timers[key] = setTimeout(pushToUrl, ms)
+      } else {
+        pushToUrl()
+      }
+    })
+  }
+
+  watch(
+    () => ({ ...route.query }),
+    (newQuery) => {
+      if (isProgrammatic) return
+      isProgrammatic = true
+      let changed = false
+      for (const key of keys) {
+        const parsed = parseValue(newQuery[key], params[key]!)
+        if (refs[key]!.value !== parsed) {
+          refs[key]!.value = parsed
+          changed = true
+        }
+      }
+      nextTick(() => {
+        isProgrammatic = false
+        if (changed && options?.onRestore) {
+          options.onRestore()
+        }
+      })
+    },
+  )
+
+  return refs as StateRefs<T>
+}
+
+function parseValue(
+  raw: unknown,
+  def: ParamDef,
+): string | number {
+  const str = typeof raw === 'string' ? raw : null
+  if (str === null) return def.default
+  if (def.type === 'number' || typeof def.default === 'number') {
+    const n = Number(str)
+    return Number.isFinite(n) ? n : def.default
+  }
+  return str
+}