revert: restore full config overwrite + Common Config Snippet (revert 992dda5c)

Revert the partial key-field merging refactoring introduced in 992dda5c,
along with two dependent commits (24fa8a18, 87604b18) that referenced
the now-removed ClaudeQuickToggles component.

The whitelist-based partial merge approach had critical issues:
- Non-whitelisted custom fields were lost during provider switching
- Backfill permanently stripped non-key fields from the database
- Whitelist required constant maintenance to track upstream changes

This restores the proven "full config overwrite + Common Config Snippet"
architecture where each provider stores its complete configuration and
shared settings are managed via a separate snippet mechanism.

Reverted commits:
- 24fa8a18: context-aware JSON editor hint + hide quick toggles
- 87604b18: hide ClaudeQuickToggles when creating
- 992dda5c: partial key-field merging refactoring

Restored:
- Full config snapshot write (write_live_snapshot) for Claude/Codex/Gemini
- Full config backfill (settings_config = live_config)
- Common Config Snippet UI and backend commands
- 6 frontend components/hooks for common config editing
- configApi barrel export and DB snippet methods

Removed:
- ClaudeQuickToggles component
- write_live_partial / backfill_key_fields / patch_claude_live
- All KEY_FIELDS constants

src/types.ts

@@ -146,10 +146,6 @@ export interface ProviderMeta {
   // - "anthropic": 原生 Anthropic Messages API 格式，直接透传
   // - "openai_chat": OpenAI Chat Completions 格式，需要格式转换
   apiFormat?: "anthropic" | "openai_chat";
-  // Claude 认证字段名（仅 Claude 供应商使用）
-  // - "ANTHROPIC_AUTH_TOKEN" (默认): 大多数第三方/聚合供应商
-  // - "ANTHROPIC_API_KEY": 少数供应商需要原生 API Key
-  apiKeyField?: "ANTHROPIC_AUTH_TOKEN" | "ANTHROPIC_API_KEY";
 }
 
 // Skill 同步方式
@@ -160,11 +156,6 @@ export type SkillSyncMethod = "auto" | "symlink" | "copy";
 // - "openai_chat": OpenAI Chat Completions 格式，需要格式转换
 export type ClaudeApiFormat = "anthropic" | "openai_chat";
 
-// Claude 认证字段类型
-// - "ANTHROPIC_AUTH_TOKEN": 大多数第三方/聚合供应商使用（默认）
-// - "ANTHROPIC_API_KEY": 少数供应商需要原生 API Key
-export type ClaudeApiKeyField = "ANTHROPIC_AUTH_TOKEN" | "ANTHROPIC_API_KEY";
-
 // 主页面显示的应用配置
 export interface VisibleApps {
   claude: boolean;