feat(portal): season thumbnails in the season dropdown + PR #1628 follow-ups (#1633)

* feat(portal): season thumbnails in the season dropdown + PR #1628 follow-ups

Follow-ups to the season posters shipped in #1628:

- The >6-seasons dropdown (`SeasonTabsComponent`) now carries a 28×42
  season thumbnail at the start of each menu row that has a poster and in
  the closed trigger for the selected season, fed by a new `seasonPosters`
  input from the season container and the fullscreen episode panel. Rows
  without a poster get no placeholder, a failed image is dropped, and the
  pill row stays text-only as the design review decided.
- The fullscreen season strip's episode count uses its own
  `PORTALS.EPISODE_COUNT_ONE/OTHER` keys instead of borrowing the download
  manager's; all 18 locales filled through the i18n merger from their
  existing `DOWNLOADS.EPISODE_COUNT_*` translations.
- The Stalker mock's serve targets no longer pin `PORT` (an nx:run-commands
  `env` entry overrides the shell), and `main.ts` resolves `PORT`, then the
  Playwright-side `MOCK_PORT` alias, then 3210 — so `MOCK_PORT=3310` now
  relocates the whole E2E run. The Xtream mock honours `XTREAM_MOCK_PORT`
  the same way.
- `resolveAutoSelectedSeason` gets a direct spec covering every branch.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix(xtream-mock): mint marketing asset URLs on the port the server bound

Greptile P1 on #1633: the listener honoured `XTREAM_MOCK_PORT`, but
`marketingAssetOrigin()` still read `PORT` alone, so a run relocated only
through the alias sent every poster/backdrop/logo/episode URL to 3211.

One resolver (`resolveXtreamMockPortString` in `mock-port.ts`: `PORT`,
then `XTREAM_MOCK_PORT`, then 3211) now feeds the environment parser, the
marketing asset origin and the demo-guide origin fallback. A spec pins the
precedence and that `marketingAssetUrl` follows the bound port.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

.changes/portal-season-dropdown-posters.md

@@ -0,0 +1,10 @@
+---
+type: feature
+area: portal
+---
+
+Series with more than six seasons now show a small season poster in the season
+dropdown — on each row that has one and on the closed selector — so a long
+list of "Season N" entries is easier to scan. The fullscreen episode panel's
+season strip also gets its own "N episodes" translation instead of borrowing
+the download manager's.