feat(imitation): add article imitation create flow

Introduce 仿写创作: new list and create views, backend imitation service
and prompt templates, worker task routing for imitation jobs, and one-click
rewrite triggers from question citation sources. Surface source article
URL/title on article list/detail, and restrict failed articles to delete-only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/prompts/loader.go

@@ -48,6 +48,9 @@ type runtimePromptsConfig struct {
 	PromptRuleTargetPlatformSupplementFormat string                         `yaml:"prompt_rule_target_platform_supplement_format"`
 	PromptRuleSupplementHeading              string                         `yaml:"prompt_rule_supplement_heading"`
 	PromptRuleOutputRequirementsSection      string                         `yaml:"prompt_rule_output_requirements_section"`
+	ArticleImitationPromptTemplate           string                         `yaml:"article_imitation_prompt_template"`
+	ArticleImitationLocaleInstructions       map[string]string              `yaml:"article_imitation_locale_instructions"`
+	ArticleImitationSettingLabels            map[string]string              `yaml:"article_imitation_setting_labels"`
 	KnowledgePromptIntroLines                []string                       `yaml:"knowledge_prompt_intro_lines"`
 	KnowledgeSnippetLabelFormat              string                         `yaml:"knowledge_snippet_label_format"`
 	KnowledgeWebsiteMarkdown                 knowledgeWebsiteMarkdownConfig `yaml:"knowledge_website_markdown"`