feat: add social media sentiment endpoints

- /stock/{symbol}/social-sentiment -- Finnhub Reddit+Twitter sentiment
  (requires premium, gracefully degrades)
- /stock/{symbol}/reddit-sentiment -- Reddit WSB/stocks/investing
  mentions, upvotes, rank via ApeWisdom (free, no key)
- /discover/reddit-trending -- Top 25 trending stocks on Reddit
  (free, no key)

ApeWisdom provides real-time Reddit data without API key.
Finnhub social-sentiment requires premium plan but endpoint
responds gracefully with premium_required flag.

finnhub_service.py

@@ -104,6 +104,134 @@ async def get_upgrade_downgrade(
         return data if isinstance(data, list) else []
 
 
+async def get_social_sentiment(symbol: str) -> dict[str, Any]:
+    """Get social media sentiment from Reddit and Twitter.
+
+    Returns mention counts, positive/negative scores, and trends.
+    """
+    if not _is_configured():
+        return {"configured": False, "message": "Set INVEST_API_FINNHUB_API_KEY"}
+    start = (datetime.now() - timedelta(days=3)).strftime("%Y-%m-%d")
+    async with _client() as client:
+        resp = await client.get(
+            "/stock/social-sentiment",
+            params={"symbol": symbol, "from": start},
+        )
+        if resp.status_code in (403, 401):
+            logger.debug("social-sentiment requires premium, skipping")
+            return {"configured": True, "symbol": symbol, "premium_required": True, "reddit": [], "twitter": []}
+        resp.raise_for_status()
+        data = resp.json()
+        if not isinstance(data, dict):
+            return {"configured": True, "symbol": symbol, "reddit": [], "twitter": []}
+        reddit = data.get("reddit", [])
+        twitter = data.get("twitter", [])
+
+        # Compute summary stats
+        reddit_summary = _summarize_social(reddit) if reddit else None
+        twitter_summary = _summarize_social(twitter) if twitter else None
+
+        return {
+            "configured": True,
+            "symbol": symbol,
+            "reddit_summary": reddit_summary,
+            "twitter_summary": twitter_summary,
+            "reddit": reddit[-20:],
+            "twitter": twitter[-20:],
+        }
+
+
+def _summarize_social(entries: list[dict[str, Any]]) -> dict[str, Any]:
+    """Summarize social sentiment entries into aggregate stats."""
+    if not entries:
+        return {}
+    total_mentions = sum(e.get("mention", 0) for e in entries)
+    total_positive = sum(e.get("positiveScore", 0) for e in entries)
+    total_negative = sum(e.get("negativeScore", 0) for e in entries)
+    avg_score = sum(e.get("score", 0) for e in entries) / len(entries)
+    return {
+        "total_mentions": total_mentions,
+        "total_positive": total_positive,
+        "total_negative": total_negative,
+        "avg_score": round(avg_score, 4),
+        "data_points": len(entries),
+    }
+
+
+async def get_reddit_sentiment(symbol: str) -> dict[str, Any]:
+    """Get Reddit sentiment from ApeWisdom (free, no key needed).
+
+    Tracks mentions and upvotes across r/wallstreetbets, r/stocks, r/investing.
+    """
+    try:
+        async with httpx.AsyncClient(timeout=10.0) as client:
+            resp = await client.get(
+                "https://apewisdom.io/api/v1.0/filter/all-stocks/page/1"
+            )
+            resp.raise_for_status()
+            data = resp.json()
+            results = data.get("results", [])
+
+            # Find the requested symbol
+            match = next(
+                (r for r in results if r.get("ticker", "").upper() == symbol.upper()),
+                None,
+            )
+            if match is None:
+                return {
+                    "symbol": symbol,
+                    "found": False,
+                    "message": f"{symbol} not in Reddit top trending (not enough mentions)",
+                }
+
+            mentions_prev = match.get("mentions_24h_ago", 0)
+            mentions_now = match.get("mentions", 0)
+            change_pct = (
+                round((mentions_now - mentions_prev) / mentions_prev * 100, 1)
+                if mentions_prev > 0
+                else None
+            )
+            return {
+                "symbol": symbol,
+                "found": True,
+                "rank": match.get("rank"),
+                "mentions_24h": mentions_now,
+                "mentions_24h_ago": mentions_prev,
+                "mentions_change_pct": change_pct,
+                "upvotes": match.get("upvotes"),
+                "rank_24h_ago": match.get("rank_24h_ago"),
+            }
+    except Exception:
+        logger.warning("Reddit sentiment failed for %s", symbol, exc_info=True)
+        return {"symbol": symbol, "error": "Failed to fetch Reddit sentiment"}
+
+
+async def get_reddit_trending() -> list[dict[str, Any]]:
+    """Get top trending stocks on Reddit (ApeWisdom, free, no key)."""
+    try:
+        async with httpx.AsyncClient(timeout=10.0) as client:
+            resp = await client.get(
+                "https://apewisdom.io/api/v1.0/filter/all-stocks/page/1"
+            )
+            resp.raise_for_status()
+            data = resp.json()
+            return [
+                {
+                    "rank": r.get("rank"),
+                    "symbol": r.get("ticker"),
+                    "name": r.get("name"),
+                    "mentions_24h": r.get("mentions"),
+                    "upvotes": r.get("upvotes"),
+                    "rank_24h_ago": r.get("rank_24h_ago"),
+                    "mentions_24h_ago": r.get("mentions_24h_ago"),
+                }
+                for r in data.get("results", [])[:25]
+            ]
+    except Exception:
+        logger.warning("Reddit trending failed", exc_info=True)
+        return []
+
+
 async def get_sentiment_summary(symbol: str) -> dict[str, Any]:
     """Aggregate all sentiment data for a symbol into one response."""
     if not _is_configured():