feat(litigationplanner): multi-axis catalog query API (Slice B2, m/paliad#124 §18.2)

New Catalog.LookupEvents(ctx, axes, depth) method exposes a unified
graph query over paliad.deadline_rules + paliad.proceeding_types + the
deadline_concept_event_types junction. Used by the Determinator
cascade, the scenarios surface (Slice D), and any future "show me
events matching X" query — centralises a fan-out that today is
duplicated across multiple client-side paths.

Package additions (pkg/litigationplanner):
  - EventLookupAxes: optional Jurisdiction / *ProceedingTypeID / Party
    / *EventCategoryID / AppealTarget. All fields optional; the empty
    value (or nil pointer) is "no filter on this axis". Multiple
    non-zero axes apply as AND.
  - EventLookupDepth: "next" (1 hop downstream) or "all-following"
    (full chain).
  - EventMatch: Rule + ProceedingType + Priority + DepthFromAnchor +
    *ParentRuleID (populated only when the parent itself is in the
    returned set, so the frontend can render a tree).
  - Catalog interface gains LookupEvents.

paliad-side implementation (internal/services/fristenrechner.go):
  - SQL pass with progressively-built WHERE clauses (one $N
    placeholder per non-zero axis). EventCategoryID uses an EXISTS
    subquery against paliad.event_category_concepts joined via
    concept_id.
  - Post-fetch parent_id graph walk in Go for depth control. Loads
    the per-proceeding rule corpus via DeadlineRuleService.List so
    children whose parent_id is in the anchor set can be added even
    when those children don't match the axes themselves. AllFollowing
    iterates to fixpoint; Next stops after one pass.
  - DepthFromAnchor computed by walking each result row up the
    parent_id chain until it hits an anchor (iteration-bounded to
    prevent infinite loops on hypothetical cycles).
  - Unknown axis values (jurisdiction="XX", party="foo",
    appealTarget="invalid") silently fall through as "no filter on
    this axis" — a stale frontend chip should not drop the entire
    result set.
  - "published + active" gate (lifecycle_state='published' AND
    is_active=true) matches LoadProceeding's WHERE clause.
  - Results ordered by (proceeding_type_id, sequence_order) so the
    frontend can render without re-sorting.

Tests (internal/services/lookup_events_test.go):
  - Live-DB driven (skipped without TEST_DATABASE_URL, matches the
    existing TestCalculateRule pattern).
  - Cases: UPC-jurisdiction returns the UPC corpus only;
    party=defendant scopes anchor matches to defendant rules;
    unknown jurisdiction falls through; appeal_target=endentscheidung
    returns the merits rules from B1 mig 134;
    appeal_target=schadensbemessung returns empty (no rules seeded).

No schema delta. No frontend wiring (the new HTTP endpoint at
GET /api/tools/lookup-events can land in a follow-up slice — the
package + paliad-side impl are the deliverable here).

internal/services/lookup_events_test.go

@@ -0,0 +1,159 @@
+package services
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/jmoiron/sqlx"
+	_ "github.com/lib/pq"
+
+	"mgit.msbls.de/m/paliad/internal/db"
+	lp "mgit.msbls.de/m/paliad/pkg/litigationplanner"
+)
+
+// TestLookupEvents covers the multi-axis catalog query API from Slice
+// B2 (m/paliad#124 §18.2). Skipped when TEST_DATABASE_URL is unset,
+// mirroring TestCalculateRule.
+//
+// Cases:
+//   - jurisdiction=UPC, depth=all-following → every active+published
+//     UPC rule, anchor depth=1 for all (no parent_id outside the
+//     filtered set lights up depth>1 because the entire UPC subset is
+//     a single anchor cohort).
+//   - proceeding_type_id (upc.inf.cfi) + party=defendant + depth=next
+//     → defendant rules in upc.inf.cfi at depth=1 + direct children
+//     of those at depth=2.
+//   - unknown jurisdiction value → silently ignored, no filter applied.
+//   - empty axes → all rules (no filter on any axis).
+func TestLookupEvents(t *testing.T) {
+	url := os.Getenv("TEST_DATABASE_URL")
+	if url == "" {
+		t.Skip("TEST_DATABASE_URL not set — skipping live DB test")
+	}
+	if err := db.ApplyMigrations(url); err != nil {
+		t.Fatalf("apply migrations: %v", err)
+	}
+	pool, err := sqlx.Connect("postgres", url)
+	if err != nil {
+		t.Fatalf("connect: %v", err)
+	}
+	defer pool.Close()
+
+	ctx := context.Background()
+	rules := NewDeadlineRuleService(pool)
+	catalog := &paliadCatalog{rules: rules}
+
+	t.Run("jurisdiction=UPC, all-following returns the UPC corpus", func(t *testing.T) {
+		matches, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{
+			Jurisdiction: "UPC",
+		}, lp.EventLookupDepthAllFollowing)
+		if err != nil {
+			t.Fatalf("LookupEvents: %v", err)
+		}
+		if len(matches) == 0 {
+			t.Fatal("expected non-empty UPC corpus")
+		}
+		// Every match must be a UPC rule.
+		for _, m := range matches {
+			if m.ProceedingType.Jurisdiction == nil || *m.ProceedingType.Jurisdiction != "UPC" {
+				t.Errorf("non-UPC row leaked into UPC-axis query: code=%s jurisdiction=%v",
+					m.ProceedingType.Code, m.ProceedingType.Jurisdiction)
+			}
+			if m.DepthFromAnchor < 1 {
+				t.Errorf("depth=%d for rule %s, want >= 1", m.DepthFromAnchor, m.Rule.ID)
+			}
+		}
+	})
+
+	t.Run("party=defendant scopes to defendant rules", func(t *testing.T) {
+		matches, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{
+			Jurisdiction: "UPC",
+			Party:        "defendant",
+		}, lp.EventLookupDepthNext)
+		if err != nil {
+			t.Fatalf("LookupEvents: %v", err)
+		}
+		if len(matches) == 0 {
+			t.Fatal("expected at least one defendant rule across the UPC corpus")
+		}
+		// Anchor matches (depth=1) must be primary_party=defendant.
+		// Depth=2 children appear under EventLookupDepthNext only as
+		// expansion from anchors — they may carry any party.
+		for _, m := range matches {
+			if m.DepthFromAnchor != 1 {
+				continue
+			}
+			if m.Rule.PrimaryParty == nil || *m.Rule.PrimaryParty != "defendant" {
+				t.Errorf("anchor row %s (depth=1) is not defendant: %v",
+					m.Rule.Name, m.Rule.PrimaryParty)
+			}
+		}
+	})
+
+	t.Run("unknown jurisdiction value silently falls through", func(t *testing.T) {
+		matchesAll, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{},
+			lp.EventLookupDepthAllFollowing)
+		if err != nil {
+			t.Fatalf("LookupEvents (all): %v", err)
+		}
+		matchesUnknown, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{
+			Jurisdiction: "XX-not-a-real-jurisdiction",
+		}, lp.EventLookupDepthAllFollowing)
+		if err != nil {
+			t.Fatalf("LookupEvents (unknown): %v", err)
+		}
+		if len(matchesAll) != len(matchesUnknown) {
+			t.Errorf("unknown jurisdiction should fall through to no-filter; got %d vs all-axes %d",
+				len(matchesUnknown), len(matchesAll))
+		}
+	})
+
+	t.Run("appeal_target=endentscheidung returns upc.apl merits rules", func(t *testing.T) {
+		matches, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{
+			Jurisdiction: "UPC",
+			AppealTarget: lp.AppealTargetEndentscheidung,
+		}, lp.EventLookupDepthAllFollowing)
+		if err != nil {
+			t.Fatalf("LookupEvents: %v", err)
+		}
+		// Should hit the 7 rules under the unified upc.apl that
+		// carry applies_to_target={endentscheidung} (Slice B1 mig 134).
+		if len(matches) == 0 {
+			t.Fatal("expected upc.apl endentscheidung rules after B1 mig")
+		}
+		for _, m := range matches {
+			if m.DepthFromAnchor != 1 {
+				continue // children of anchors may be from other targets
+			}
+			found := false
+			for _, t := range m.Rule.AppliesToTarget {
+				if t == lp.AppealTargetEndentscheidung {
+					found = true
+					break
+				}
+			}
+			if !found {
+				t.Errorf("anchor row %s missing endentscheidung target: %v",
+					m.Rule.Name, m.Rule.AppliesToTarget)
+			}
+			if m.ProceedingType.Code != "upc.apl" {
+				t.Errorf("anchor row %s came from %s, want upc.apl",
+					m.Rule.Name, m.ProceedingType.Code)
+			}
+		}
+	})
+
+	t.Run("appeal_target=schadensbemessung returns empty (no rules seeded yet)", func(t *testing.T) {
+		matches, err := catalog.LookupEvents(ctx, lp.EventLookupAxes{
+			Jurisdiction: "UPC",
+			AppealTarget: lp.AppealTargetSchadensbemessung,
+		}, lp.EventLookupDepthAllFollowing)
+		if err != nil {
+			t.Fatalf("LookupEvents: %v", err)
+		}
+		if len(matches) != 0 {
+			t.Errorf("schadensbemessung should be empty until rules seeded; got %d rows", len(matches))
+		}
+	})
+}