Fix translate: working default backend, settings UI, outgoing translation

[MaikCZE]

Summary

Follow-up to #203, rebased onto master_new and addressing every point from SollyBunny's review there:

• The translate feature (translate.cpp) had no settings UI at all (config-var only), no way to translate your own outgoing messages, and its default backend was silently dead (ftapi.pythonanywhere.com now 404s to a generic placeholder page).
• Adds a working google backend (talks directly to the same free, unofficial Google Translate endpoint FTApi used to wrap), a full Translate section in the settings menu, and outgoing-message translation.

Changes since #203

• Google backend now POSTs in the body, not the URL query string (application/x-www-form-urlencoded) -- keeps CHttpRequest::m_aUrl's fixed 256-byte buffer well within bounds regardless of message length, instead of risking truncation on a long chat message.
• Removed the FreeTranslateAPI (ftapi) backend entirely -- its hosting is gone, and anyone wanting a self-hosted option already has the LibreTranslate backend. Removed its stale "hosting is dead" comment and its ftapi-specific auto-translate guard along with it.
• No more duplicated backend names: g_aTranslateBackends[] (translate.h/.cpp) is now the single source of truth for each backend's config value + display name, used by both CreateTranslateBackend() dispatch and the settings-menu dropdown -- the dropdown previously hardcoded its own copy of these strings.
• No more magic-number English fallback: TranslateLanguageIndex() finds English by comparing language codes instead of a hardcoded return 5, so it stays correct regardless of how a language list is edited/reordered.
• Language dropdowns are backend-scoped: Google and LibreTranslate now have their own language lists (g_aTranslateBackends[i].m_pLanguages) instead of one shared list, since Google genuinely supports far more languages than a typical self-hosted LibreTranslate instance.
• chat.cpp diff reduced to one line: outgoing translation is now CTranslate::ChatDoTranslateOutgoing(), returning bool and chained as another else if alongside ChatDoBinds/ChatDoSpecId instead of a separate nested if/else block.
• Simplified the "too many jobs in flight" comment that read oddly in the original PR.

Test plan

• Compiled clean with MSVC 19.51 (Release, Ninja) -- full DDNet.exe build, zero errors/warnings from any touched file
• Rebased cleanly onto master_new (cherry-picked with no conflicts)
• Would appreciate a look at the Google endpoint-in-body change specifically, since I can't independently confirm the endpoint accepts POST the same way it accepts GET query params

Supersedes #203.

🤖 Generated with Claude Code

[SollyBunny]

I dislike the large number of globals and separate vars for arrays and the size
I suggest:

1. Keeping g_aTranslateBackends, but using inlining g_NumTranslateBackends
2. Move the values from the individual classes to this array (so the classes no longer hold it)
3. Change the language list to be std::vectors

Check style is failing (run scripts/fix_style.py), and also check other CI when it completes

[MaikCZE]

Addressed all three points from the review, plus check-style:

1. g_aTranslateBackends stays as-is (now std::array<STranslateBackendInfo, 2>); g_NumTranslateBackends is gone, callers use g_aTranslateBackends.size() directly.
2. Backend name/value no longer live in the individual classes -- removed StaticName()/StaticValue()/the Name() overrides. ITranslateBackend now takes its name once at construction (sourced from the matching g_aTranslateBackends entry via CreateTranslateBackend()), so the array is the single place that data exists.
3. Both language lists are now std::vector<STranslateLanguage> (STranslateBackendInfo::m_vLanguages), not raw C arrays.

check-style: ran scripts/fix_style.py (clang-format 20) -- also picked up one pre-existing, unrelated style issue in chat.cpp's AddLine() (regex chat-ignore lambda) since formatting runs per-file, not per-diff-line.

check-clang-tidy's remaining failures (mumble.h, discord.cpp, client.cpp, menus_start.cpp, menus_settings.cpp) are pre-existing on master_new itself -- confirmed via master_new's own most recent check-runs already showing check-clang-tidy failing, and none of those files are touched by this PR. Left alone as out of scope here.

Rebuilt clean with MSVC 19.51 (Release, Ninja) after each change, zero errors/warnings.

🤖 Addressed by Claude Code

[SollyBunny]

This looks good to me, but I still need to test it #208