chore: 清理配置文件并移动功能创意文档

- .gitignore 添加 .env，防止密钥泄露
- 删除误提交的 backend/.env
- TTS 模型名修正为 mimo-v2.5-tts
- 功能创意.md 移至 docs/10-功能创意.md

.gitignore

@@ -7,6 +7,7 @@ backend/bin/
 backend/server
 
 # ---- 环境变量 ----
+.env
 .env.local
 .env.*.local
 

backend/.env

@@ -1,17 +0,0 @@
-# ---- AI 服务 API Key ----
-CAMTALK_AI_LLM_API_KEY=sk-ws-H.REHELLY.C4s3.MEUCIQCRee37XWEKp2szaxVLFDtR1rxNNsf372zMvCR0Xl6UvQIgZgvhRTvaa1FmhbCQJgaHu4Jny29AQkn01-3hX9CWBOg
-CAMTALK_AI_STT_API_KEY=sk-c3jhv58rr5djhxw398w2rrij5tfpnpdgxqq1bojagshzviah
-CAMTALK_AI_TTS_API_KEY=tp-c9e7scwfx94qvqyhpnahnw8uaiya01za2qzvg4xe24rp3xiv
-
-# ---- 可选覆盖（默认值见 config.yaml）----
-# CAMTALK_AI_LLM_MODEL=qwen3-vl-plus
-# CAMTALK_AI_LLM_ENDPOINT=https://api.openai.com/v1
-# CAMTALK_AI_LLM_TIMEOUT=10
-# CAMTALK_AI_STT_ENDPOINT=wss://api.deepgram.com/v1/listen
-# CAMTALK_AI_TTS_ENDPOINT=https://api.openai.com/v1
-# CAMTALK_AI_TTS_VOICE=alloy
-# CAMTALK_AI_TTS_SPEED=1.0
-# CAMTALK_AI_TTS_TIMEOUT=5
-
-# ---- 应用 ----
-# APP_ENV=dev

backend/config.yaml

@@ -27,7 +27,7 @@ ai:
     timeout: 30
   tts:
     provider: Xiaomi MiMo
-    model: mimo-v2.5
+    model: mimo-v2.5-tts
     voice: alloy
     speed: 1.0
     endpoint: "https://token-plan-cn.xiaomimimo.com/v1"