feat(analytics): sticky range + sortable per-model table columns

[jasnoorgill]

Summary

Two small but related client-side improvements to the analytics page,
shipped together because they share infrastructure and would otherwise
conflict on the same lines of AnalyticsPage.tsx:

1. Sticky time range — the selected 24h/7d/30d/90d range now persists
   in localStorage so reloads and new sessions land on the user's
   last choice.
2. Sortable per-model table — every column in the "per-model
   breakdown" table (except pinned, which renders —) is now
   clickable to sort. 3-state cycle: unsorted (API order) → asc → desc → unsorted. Last selection persists in localStorage too.

Both use the same persistence shape as the existing theme toggle
and freellmapi.locale preference. Same useState + useEffect
pattern, same try/catch on every storage access.

Why combined

Originally shipped as PR #462 (sticky range only). Adding the sort
work on top of #462's branch required a rebase that would have
re-written #462's commits — at that point the cleanest move was a
single PR covering both. The two features are thematically adjacent
(analytics-page UX) and small individually, so combining avoids
two PRs reviewing the same file.

Rebase onto current origin/main (9858eee)

This is a re-submission of #463 (which was based on a stale origin/main
snapshot @ 9048dd6). The analytics page changed significantly upstream
since the original PR — main now uses a <SegmentedControl> shared
component for the range selector, TimeRange widens to include 90d,
stats load via skeletons, and several i18n keys changed. The
localStorage pattern itself is unchanged.

Two conflicts during cherry-pick, both resolved in favor of keeping
both changes:

1. useState<TimeRange>('7d') line — kept the PR's loadStoredRange
   init and added upstream's const [now] capture alongside it.
2. byModel.map((m, i) => ( vs PR's sortedByModel.map(...) —
   took the PR's sort-applied version.

Also: added '90d' to the TIME_RANGES allowlist (the PR pre-dated
that range option; without it, a user who selected 90d would have
their sticky selection silently dropped to '7d' on the next reload).

Changes

File	Change
client/src/pages/AnalyticsPage.tsx	+189 / -11. Added useMemo to imports, STORAGE_KEY/loadStoredRange/sort types, SortableHeader helper component, sort state + persistence effect, onHeaderClick reducer, sortedByModel memoized sort, replaced 8 of 9 column headers with <SortableHeader> (pinned stays static), added lucide-react ArrowUp/ArrowDown/ChevronsUpDown imports.

1 file, +189 / -11 across 2 commits.

Sort behavior

State	Indicator	Order
Unsorted	ChevronsUpDown (faded)	API-returned (requests DESC)
Asc	ArrowUp	A→Z / 0→9
Desc	ArrowDown	Z→A / 9→0

• Click another column → starts at asc on the new column.
• Click the same column three times → back to API order, storage
  key removed.
• Null values sort last in both directions (Excel/Sheets convention).
• Right-aligned columns flip the indicator with flex-row-reverse so
  the label stays closest to the data.
• aria-sort attribute is set on each header button for screen readers.

pinned is intentionally not sortable: it renders — for zero-pinned
rows, and the 0/>0 distinction is meaningless to sort on.

localStorage keys

Key	Value	When written
freellmapi.analytics.range	'24h' | '7d' | '30d' | '90d'	On range change
freellmapi.analytics.byModelSort	{"column": "...", "direction": "asc"|"desc"} or absent	On sort change (removed on unsort)

Both keys are validated against an allowlist on read so a corrupted
entry falls back to the default rather than crashing the page. Both
writes are wrapped in try/catch for SSR / private-mode safety.

Test plan

• cd client && npx tsc -b — clean, 0 errors.
• cd client && npm run build — ✓ built in 8.72s.
• Bundle contains both storage keys + the icon imports:
  grep -oE 'freellmapi\.analytics\.[a-zA-Z]+' client/dist/assets/index-*.js
  returns both freellmapi.analytics.range and
  freellmapi.analytics.byModelSort.

Manual smoke (assumes the user runs locally):

1. Open /analytics, click 30d. Hard-reload — opens on 30d.
2. Click any column header (e.g. "Latency") — sorts asc, indicator
   shows ↑, header text darkens.
3. Click again — sorts desc, indicator shows ↓.
4. Click a third time — back to API order, indicator faded.
5. Click a different column — starts at asc on the new column.
6. Reload — your last sort is restored.
7. Hard-reload after clicking through to unsort — the key is
   removed from localStorage, the page loads in API order.

Compatibility

No breaking changes. Defaults are unchanged (7d range, API-natural
row order). The persistence is additive. New localStorage keys
are namespaced under freellmapi.* per the existing convention.

Supersedes

Closes #462 (the sticky-range half of this work is included here).
This PR supersedes #463, which was the original submission based on
a stale main snapshot and is now CLOSED.

References operator sessions 2026-07-04 / 2026-07-07. No upstream
issue number yet — happy to file one if requested.