Fix MiniMax CN Token Plan web fetch with token-plan endpoints (#254)

[Finesssee]

Problem

A MiniMax China-mainland Token Plan user (TokenPlanPlus annual membership) has no coding-plan subscription, so the legacy endpoint GET /v1/api/openplatform/coding_plan/remains answers HTTP 200 with base_resp.status_code=2062 / status_msg="no active token plan subscription". 0.47.0 surfaced that as a fatal fetch error.

Upstream (steipete/CodexBar) has zero support for the token-plan endpoints — this is implemented from the reporter's live evidence.

Fix (rust/src/providers/minimax only)

• coding_plan::is_token_plan_without_coding_plan — matches ProviderError::Other messages containing "token plan" (case-insensitive), i.e. exactly the 2062 path through the existing remains parser.
• fetch_with_cookie wraps the coding-plan call: on that error it falls back to a new token-plan path; auth rejection stays AuthRequired; when all token-plan endpoints are empty the original coding-plan error propagates unchanged.
• New token-plan path (fetch_token_plan_with_cookie), all on the www host with the fetch_remains_once request envelope:
  • GET /v1/api/openplatform/charge/token_plan/usage — 401/403 → AuthRequired, other non-2xx/parse failures swallowed; body parsed with the shared parse_coding_plan_value (charge-API family shares the model_remains/services schema).
  • GET /backend/account/token_plan/usage_summary — lenient parse of total_days/active_days/total_token_consumed (numbers or numeric strings, root or "data") → informational "Token Plan" extra window (123,456 tokens · 5 / 30 days active) or summary-only snapshot.
  • GET /backend/account/token_plan_credit — plan title (current_subscribe_title/…/current_combo_card.title/title) → login method.
• Same best-effort billing enrichment as the coding-plan path afterwards. Cookies never logged.

Fixes #254

Tests

• cargo test --manifest-path rust/Cargo.toml minimax — 36 passed, 0 failed (8 new: predicate incl. the reporter's 2062 fixture, summary/title parsing, charge-usage fixture → 5h primary at 2% + unlimited weekly end-to-end, full/summary-only/row-less/all-absent assembly, original-error fallback).
• Full cargo test --manifest-path rust/Cargo.toml — 926 passed, 0 failed.
• cargo clippy --workspace --all-targets -- -D warnings — clean. cargo fmt --all applied.

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