Add missing case_precedents CRUD functions to db module

Four functions were called by tools/precedents.py but never implemented
in services/db.py: create_case_precedent, list_case_precedents,
delete_case_precedent, search_precedent_library. This caused 500 errors
on the /api/cases/{n}/precedents endpoint.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/db.py

@@ -1066,6 +1066,91 @@ async def search_precedents(
     return results[:limit]
 
 
+# ── Case precedents (CRUD) ────────────────────────────────────────
+
+
+async def create_case_precedent(
+    case_id: UUID,
+    quote: str,
+    citation: str,
+    section_id: str | None = None,
+    chair_note: str = "",
+    pdf_document_id: UUID | None = None,
+    practice_area: str | None = None,
+) -> dict:
+    """Insert a new precedent attached to a case."""
+    pool = await get_pool()
+    row = await pool.fetchrow(
+        """
+        INSERT INTO case_precedents
+            (case_id, section_id, quote, citation, chair_note, pdf_document_id, practice_area)
+        VALUES ($1, $2, $3, $4, $5, $6, $7)
+        RETURNING *
+        """,
+        case_id, section_id, quote, citation, chair_note, pdf_document_id, practice_area,
+    )
+    return dict(row)
+
+
+async def list_case_precedents(case_id: UUID) -> list[dict]:
+    """List all precedents attached to a case, ordered by section then creation time."""
+    pool = await get_pool()
+    rows = await pool.fetch(
+        """
+        SELECT id, case_id, section_id, quote, citation, chair_note,
+               pdf_document_id, practice_area, created_at, updated_at
+        FROM case_precedents
+        WHERE case_id = $1
+        ORDER BY section_id NULLS LAST, created_at
+        """,
+        case_id,
+    )
+    return [dict(r) for r in rows]
+
+
+async def delete_case_precedent(precedent_id: UUID) -> bool:
+    """Delete a precedent attachment by ID. Returns True if deleted."""
+    pool = await get_pool()
+    result = await pool.execute(
+        "DELETE FROM case_precedents WHERE id = $1", precedent_id
+    )
+    return result == "DELETE 1"
+
+
+async def search_precedent_library(
+    query: str, practice_area: str = "", limit: int = 10,
+) -> list[dict]:
+    """Search all precedents across cases by citation or quote text."""
+    pool = await get_pool()
+    pattern = f"%{query}%"
+    if practice_area:
+        rows = await pool.fetch(
+            """
+            SELECT id, case_id, section_id, quote, citation, chair_note,
+                   practice_area, created_at
+            FROM case_precedents
+            WHERE (citation ILIKE $1 OR quote ILIKE $1)
+              AND practice_area = $2
+            ORDER BY created_at DESC
+            LIMIT $3
+            """,
+            pattern, practice_area, limit,
+        )
+    else:
+        rows = await pool.fetch(
+            """
+            SELECT id, case_id, section_id, quote, citation, chair_note,
+                   practice_area, created_at
+            FROM case_precedents
+            WHERE citation ILIKE $1 OR quote ILIKE $1
+            ORDER BY created_at DESC
+            LIMIT $2
+            """,
+            pattern, limit,
+        )
+    return [dict(r) for r in rows]
+
+
 # ── Chair feedback ────────────────────────────────────────────────
 
 async def record_chair_feedback(