feat: add APA citation field to enrichment output

Extend Gemini 2.5 Flash prompt to also extract APA 7th edition
citation string per result. Bump max_tokens 512 → 1024 to
accommodate the longer JSON response.

src/enricher.py

@@ -82,6 +82,7 @@ You are an information extractor. Analyze the web page content below and return
 - "author": author or organization name, or null if not found (string | null)
 - "tags": list of 3-5 relevant keywords (string[])
 - "content_type": one of "article", "documentation", "news", "forum", "code", "video", "other" (string)
+- "citation": APA 7th edition citation string for this source (string). Format: Author/Org. (Year, Month Day). Title. Site Name. URL — use "n.d." if date unknown, omit fields that cannot be determined.
 
 Title: {title}
 URL: {url}
@@ -110,7 +111,7 @@ def enrich_result(title: str, url: str, snippet: str) -> dict:
         client = _get_llm_client()
         req = GenericChatRequest(
             messages=[UserMessage(content=[TextContent(text=prompt)])],
-            max_tokens=512,
+            max_tokens=1024,
             temperature=0,
         )
         det = ChatDetails(
@@ -132,6 +133,7 @@ def enrich_result(title: str, url: str, snippet: str) -> dict:
             "author": None,
             "tags": [],
             "content_type": "other",
+            "citation": None,
             "_error": str(exc),
         }