fix(compiler): React Compiler safety triage — 5 categories cleared

Cleared 4 rule buckets (37 violations, including 5 real bugs) and
silenced 1 informational bucket from the Next 16 / react-hooks v7
upgrade. Cleared rules promoted from `warn` back to `error` so new
regressions block CI.

Real bug fixes:
- `interest-contact-log-tab.tsx`: `useMemo` used for side effects
  (5 setState calls inside a memo body); converted to `useEffect`.
- `PieChart.tsx`: cumulative `let angle` mutation in a render-phase
  `map`; converted to `reduce` so the slice array is built without
  re-assignment.
- `documents-hub.tsx`: `useMemo(() => ({ count: 0 }))` used as a
  mutable drag counter; converted to `useRef`.
- `notes-list.tsx`: `Date.now()` read during render for note-edit
  countdown (impure) → pinned to a `now` state ticked every 30s.
- `onboarding-checklist.tsx` / `user-profile.tsx` /
  `user-settings.tsx`: `useEffect(() => void load(), [])` with the
  `load` function declared AFTER the effect — relied on hoisting,
  trips Compiler's "access before declared" rule. Declared inside
  the effect.

Pattern fixes (intentional cache-via-ref → state or layout-effect):
- 6 `ref.current = x` writes during render moved into layout
  effects (`use-realtime-invalidation`, `settings-form-card`,
  `inbox`).
- 3 `ref.current` reads during render (search totals cache,
  scanner file ref) rewritten to backed-by-state.
- `use-is-mobile.ts` rewritten on `useSyncExternalStore` to avoid
  the SSR-then-rehydrate setState dance.
- `use-notifications.ts` rewritten to write socket pushes directly
  into the React Query cache via `setQueryData`, removing a local
  state mirror.

Rule config (`eslint.config.mjs`):
- `react-hooks/purity` → error (was warn, cleared)
- `react-hooks/set-state-in-render` → error (was warn, cleared)
- `react-hooks/immutability` → error (was warn, cleared)
- `react-hooks/refs` → error (was warn, cleared)
- `react-hooks/incompatible-library` → off (informational only)
- `react-hooks/set-state-in-effect` → warn (51 remaining, all the
  useEffect→fetch→setState data-fetch pattern; migration to
  useQuery tracked in BACKLOG)

Verified: tsc clean, eslint 0 errors / 69 warnings (down from 105),
vitest 1315/1315, next build green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/settings/user-profile.tsx

@@ -35,15 +35,14 @@ export function UserProfile() {
   } | null>(null);
 
   useEffect(() => {
+    async function load() {
+      const res = await apiFetch<{ data: { user?: MeUser } }>('/api/v1/me');
+      setMe(res.data.user ?? null);
+      setDisplayName(res.data.user?.name ?? '');
+    }
     void load();
   }, []);
 
-  async function load() {
-    const res = await apiFetch<{ data: { user?: MeUser } }>('/api/v1/me');
-    setMe(res.data.user ?? null);
-    setDisplayName(res.data.user?.name ?? '');
-  }
-
   async function saveProfile() {
     setSavingProfile(true);
     setProfileMessage(null);

src/components/settings/user-settings.tsx

@@ -67,29 +67,28 @@ export function UserSettings() {
   }, []);
 
   useEffect(() => {
+    async function loadProfile() {
+      const res = await apiFetch<{ data: MeResponse }>('/api/v1/me', { method: 'GET' });
+      setFirstName(res.data.profile?.firstName ?? '');
+      setLastName(res.data.profile?.lastName ?? '');
+      // Display name is the override; fall back to user.name if profile
+      // doesn't carry one (e.g. legacy rows pre-Wave 10).
+      setDisplayName(res.data.profile?.displayName ?? res.data.user?.name ?? '');
+      setEmail(res.data.user?.email ?? '');
+      setOriginalEmail(res.data.user?.email ?? '');
+      setUsername(res.data.profile?.username ?? '');
+      setOriginalUsername(res.data.profile?.username ?? '');
+      setCountry(res.data.preferences?.country ?? null);
+      // Fall back to the browser-detected zone when no value has been
+      // saved yet — first-time users land on a sensible default rather
+      // than an empty picker. Doesn't overwrite an explicit choice.
+      setTimezone(res.data.preferences?.timezone ?? detectedTz ?? null);
+      const fid = res.data.profile?.avatarFileId ?? null;
+      setAvatarFileId(fid);
+      setAvatarUrl(fid ? `/api/v1/files/${fid}/preview` : null);
+    }
     void loadProfile();
-  }, []);
-
-  async function loadProfile() {
-    const res = await apiFetch<{ data: MeResponse }>('/api/v1/me', { method: 'GET' });
-    setFirstName(res.data.profile?.firstName ?? '');
-    setLastName(res.data.profile?.lastName ?? '');
-    // Display name is the override; fall back to user.name if profile
-    // doesn't carry one (e.g. legacy rows pre-Wave 10).
-    setDisplayName(res.data.profile?.displayName ?? res.data.user?.name ?? '');
-    setEmail(res.data.user?.email ?? '');
-    setOriginalEmail(res.data.user?.email ?? '');
-    setUsername(res.data.profile?.username ?? '');
-    setOriginalUsername(res.data.profile?.username ?? '');
-    setCountry(res.data.preferences?.country ?? null);
-    // Fall back to the browser-detected zone when no value has been saved
-    // yet — first-time users land on a sensible default rather than an
-    // empty picker. Doesn't overwrite an explicit choice.
-    setTimezone(res.data.preferences?.timezone ?? detectedTz ?? null);
-    const fid = res.data.profile?.avatarFileId ?? null;
-    setAvatarFileId(fid);
-    setAvatarUrl(fid ? `/api/v1/files/${fid}/preview` : null);
-  }
+  }, [detectedTz]);
 
   // When the user picks a country and no timezone is set, suggest the
   // primary zone for that country. Doesn't fight an explicit timezone