feat: add RAG search endpoint with content extraction

- Add /rag/search endpoint for web, news, and image search via SearXNG
- Add /content/extract and /content/extract/batch endpoints
- Add ContentExtractor client using Trafilatura for content extraction
- Enhance HybridRAG web search with full content extraction
- Add Redis caching for search results
- Add new configuration options for search and extraction timeouts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/models/content.py

@@ -0,0 +1,69 @@
+"""
+Content extraction models for Library Desk.
+
+Pydantic models for content extraction requests and responses.
+"""
+
+from typing import Optional, List
+from pydantic import BaseModel, Field
+
+
+class ContentExtractionResult(BaseModel):
+    """Result of extracting content from a single URL."""
+
+    url: str = Field(..., description="The URL that was processed")
+    title: Optional[str] = Field(None, description="Page title if extracted")
+    content: str = Field("", description="Extracted main text content")
+    author: Optional[str] = Field(None, description="Author if available")
+    date: Optional[str] = Field(None, description="Publication date if available (ISO format)")
+    language: Optional[str] = Field(None, description="Detected language code")
+    success: bool = Field(..., description="Whether extraction succeeded")
+    error: Optional[str] = Field(None, description="Error message if extraction failed")
+
+
+class ContentExtractionRequest(BaseModel):
+    """Request to extract content from a single URL."""
+
+    url: str = Field(..., min_length=1, description="URL to extract content from")
+    include_metadata: bool = Field(default=True, description="Include title, author, date metadata")
+    max_length: Optional[int] = Field(
+        None,
+        ge=100,
+        le=50000,
+        description="Override default max content length"
+    )
+
+
+class ContentExtractionResponse(BaseModel):
+    """Response for single URL extraction."""
+
+    result: ContentExtractionResult
+    extraction_time_ms: int = Field(..., ge=0, description="Time taken to extract content")
+
+
+class BatchContentExtractionRequest(BaseModel):
+    """Request to extract content from multiple URLs."""
+
+    urls: List[str] = Field(
+        ...,
+        min_length=1,
+        max_length=20,
+        description="URLs to extract content from (max 20)"
+    )
+    include_metadata: bool = Field(default=True, description="Include title, author, date metadata")
+    max_length: Optional[int] = Field(
+        None,
+        ge=100,
+        le=50000,
+        description="Override default max content length"
+    )
+
+
+class BatchContentExtractionResponse(BaseModel):
+    """Response for batch URL extraction."""
+
+    results: List[ContentExtractionResult]
+    total_urls: int = Field(..., ge=0, description="Total number of URLs processed")
+    successful: int = Field(..., ge=0, description="Number of successful extractions")
+    failed: int = Field(..., ge=0, description="Number of failed extractions")
+    extraction_time_ms: int = Field(..., ge=0, description="Total time for batch extraction")