feat: inline edit for patterns in library (name, description, category, direction, regime)

- Backend: PATCH /api/patterns/custom/{id} — partial update, only provided fields changed
- useApi.ts: usePatchPattern mutation hook
- PatternCard: pencil icon (non-builtin only) → edit mode with inline inputs for name, description, direction (select), category, and #regime; ✓/✗ buttons to save or cancel; card border highlights blue while editing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/patterns.py

@@ -61,6 +61,34 @@ def update_pattern(pat_id: str, req: PatternRequest):
     return {"id": pat_id, "status": "updated"}
 
 
+class PatternPatchRequest(BaseModel):
+    name: Optional[str] = None
+    description: Optional[str] = None
+    category: Optional[str] = None
+    signal_direction: Optional[str] = None
+    regime_tag: Optional[str] = None
+
+
+@router.patch("/custom/{pat_id}")
+def patch_pattern(pat_id: str, req: PatternPatchRequest):
+    """Partial update — only provided fields are changed."""
+    from services.database import get_conn
+    conn = get_conn()
+    if not conn.execute("SELECT id FROM custom_patterns WHERE id=?", (pat_id,)).fetchone():
+        conn.close()
+        raise HTTPException(404, "Pattern not found")
+    updates = {k: v for k, v in req.model_dump().items() if v is not None}
+    if updates:
+        set_clause = ", ".join(f"{k}=?" for k in updates)
+        conn.execute(
+            f"UPDATE custom_patterns SET {set_clause}, updated_at=datetime('now') WHERE id=?",
+            list(updates.values()) + [pat_id],
+        )
+        conn.commit()
+    conn.close()
+    return {"id": pat_id, "status": "updated", "fields": list(updates.keys())}
+
+
 @router.delete("/purge-all")
 def purge_all_patterns():
     """Delete ALL custom/backtested patterns from the pattern library."""