feat(chat): optimistic local echo + moderation delivery notices (v1)

[ChronoFinale]

What

Client half of the chat-moderation v1 rollout — pairs with the relay bridge PR (Balatro-Multiplayer/BalatroMultiplayerAPI-Server#40):

• Optimistic local echo — the sender's message renders instantly on enter; the MQTT self-echo is dropped so it never double-renders. Recipients are unaffected (they only ever receive the moderated form).
• "not delivered" — if moderation blocks the message, the sender's echo is replaced with a notice that other players never saw it.
• "delivered as …" — if moderation rewrote it, the sender sees exactly what was delivered (the relay returns publishText in the /chat response).
• MPAPI.chat.mute_player local mute, bridge-guarded: the aggregate mute signal only fires when the v2 intake bridge exists, so on the v1 relay it's a clean local-only mute.

With the relay's MODERATION_SERVICE_URL unset, all of this degrades gracefully — messages just deliver as they do today.

Stacking

⚠️ Depends on #10 (api_client FIFO fix) — this branch is stacked on it, so the diff currently shows both. Review the last two commits only; once #10 merges I'll rebase and this collapses to just the chat work.

Testing

Tested end-to-end in-game against the live moderation service through the relay bridge: instant echo, block notice, rewrite notice ("suck my cock" → delivered as: suck my cocktail), and preset messages surviving a simulated moderation outage.