feat(search): add header global search (Phase A) — cases + precedents + docs

Adds an always-visible debounced search input in the AppShell header
that fans out to three independent sources in parallel and renders
per-source result groups with their own loading/empty/error states:

- /api/search/cases (NEW): SQL ILIKE on case_number, address, parties,
  title, subject. Returns small projections, no embeddings needed.
- /api/precedent-library/search (existing): semantic over case-law
  halachot + passages.
- /api/search (existing): semantic over case documents + past decisions.

Cmd/Ctrl+K focuses the input; Esc and click-outside close the panel.
This is Phase A of the header redesign — the bar layout itself is
unchanged; row grouping + dynamic context follow in Phase B.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/app.py

@@ -1387,6 +1387,55 @@ async def api_case_search(case_number: str, query: str, limit: int = 10):
         return {"message": result}
 
 
+@app.get("/api/search/cases")
+async def api_search_cases(q: str, limit: int = 10):
+    """Lightweight SQL search over cases — by case number, address, parties, title.
+
+    Powers the global-search dropdown in the header. Returns small projections,
+    not full case objects.
+    """
+    q = q.strip()
+    if len(q) < 2:
+        return {"items": [], "count": 0}
+
+    needle = f"%{q}%"
+    prefix = f"{q}%"
+
+    pool = await db.get_pool()
+    async with pool.acquire() as conn:
+        rows = await conn.fetch(
+            """
+            SELECT case_number, title, property_address, status,
+                   practice_area, appeal_subtype, updated_at
+              FROM cases
+             WHERE case_number       ILIKE $1
+                OR property_address  ILIKE $1
+                OR title             ILIKE $1
+                OR subject           ILIKE $1
+                OR appellants::text  ILIKE $1
+                OR respondents::text ILIKE $1
+             ORDER BY
+                   CASE WHEN case_number ILIKE $2 THEN 0 ELSE 1 END,
+                   updated_at DESC NULLS LAST
+             LIMIT $3
+            """,
+            needle, prefix, limit,
+        )
+
+    items = [
+        {
+            "case_number":      r["case_number"],
+            "title":            r["title"],
+            "property_address": r["property_address"],
+            "status":           r["status"],
+            "practice_area":    r["practice_area"],
+            "appeal_subtype":   r["appeal_subtype"],
+        }
+        for r in rows
+    ]
+    return {"items": items, "count": len(items)}
+
+
 @app.get("/api/cases/{case_number}/template")
 async def api_case_template(case_number: str):
     """Get outcome-aware decision template for a case."""