fix: pass API key for gemini/openai/openrouter in generate_candidates

[looksg00d]

Bug

Selecting Gemini, OpenAI, or OpenRouter as the LLM provider in Settings and entering an API key there has no effect on moment detection — it still fails with:

Set OPENROUTER_API_KEY or supply OpenRouter API Key to generate candidates.

(or the equivalent for GEMINI_API_KEY / OPENAI_API_KEY), even though the key is set in the UI, and even though the .env var isn't set at all.

Root cause

In src/main.tsx, both call sites of generate_candidates (in confirmImport() and moments()) resolve the outgoing apiKey with:

const activeKey = llmEngine === "claude" ? anthropicKey.trim() : (llmEngine === "deepseek" ? deepseekKey.trim() : "");

This only handles claude and deepseek; for gemini, openai, and openrouter it silently falls through to "" → sent as apiKey: null → the Rust side (lib.rs, generate_candidates) then only has the env var to fall back on, and errors if it isn't set.

Note runAutoPipeline() already has the correct full mapping a few lines above (used just for the pre-flight "is a key configured" check), it just was never mirrored into the two actual invoke("generate_candidates", ...) calls.

Fix

Mirror the same per-provider key mapping used in runAutoPipeline() into both generate_candidates call sites:

const activeKey =
  llmEngine === "claude" ? anthropicKey.trim() :
    llmEngine === "deepseek" ? deepseekKey.trim() :
      llmEngine === "gemini" ? geminiKey.trim() :
        llmEngine === "openai" ? openaiKey.trim() :
          llmEngine === "openrouter" ? openrouterKey.trim() : "";

Test plan

Ran into this myself with an OpenRouter key set only in Settings (no .env) — reading through the code confirmed activeKey was resolving to "" for the openrouter case, which matched the symptom exactly. The fix just mirrors the mapping already used (and working) in runAutoPipeline() a few lines above onto the two call sites that were missing it, so the logic itself isn't new/untested, just newly applied in these two spots. I have not personally re-run the full pipeline end-to-end against Gemini/OpenAI/OpenRouter after applying the fix to confirm candidate generation succeeds — flagging that in case a maintainer wants to verify before merging.