feat: L1->L2 agent pool and routing engine for voice escalation

Replaces the hardcoded single-extension redirect for AI->human call
escalation with a real Agent Pool + Routing Engine:

- agents/escalations/routing_rules tables (migration 0031), asterisk_call_links
  gains tenant_id/current_level/required_skills_json/priority.
- services/routing_service/engine.py: level/tenant/skill filtered agent
  selection with atomic (CAS) reservation, no double-booking.
- routing-service: /agents CRUD + /internal/routing/reserve-agent and
  /internal/routing/release-agent.
- asterisk-bridge-service: voice_ai.request_handoff now uses the Routing
  Engine automatically for any queue_code configured in
  ASTERISK_QUEUE_LEVEL_MAP_JSON (all other queue_codes keep the existing
  static ASTERISK_TRANSFER_TARGET_MAP_JSON behavior unchanged); new
  POST /asterisk/live-calls/{call_id}/escalations entrypoint; agent is
  released back to AVAILABLE and the escalation closed when the call ends.

Targets the Tele2 Kazgaz DID +77476456048 (from-tele2-kazgaz context) as the
first queue wired to real L2 routing instead of AI-only.

Known gap (documented in docs/architecture/l1-l2-routing-engine.md):
automatic no-answer retry-to-next-agent needs a small, separately reviewed
dialplan change and is left for a follow-up MR rather than guessed at blind.

Tests: services/routing_service/engine.py covered by
tests/test_routing_engine.py (selection filtering, atomic reservation,
release); existing test_asterisk_bridge_service.py and
test_routing_service_pg_counter.py suites still pass unmodified.

services/shared/sql_init.py

@@ -471,6 +471,25 @@ def _apply_runtime_schema_compatibility() -> None:
                         "ON asterisk_call_links(customer_name_resolved_at)"
                     )
                 )
+            _add_column_if_missing(conn, columns, "asterisk_call_links", "tenant_id", "VARCHAR(64)")
+            _add_column_if_missing(conn, columns, "asterisk_call_links", "current_level", "VARCHAR(16)")
+            _add_column_if_missing(conn, columns, "asterisk_call_links", "required_skills_json", "TEXT DEFAULT '[]'")
+            _add_column_if_missing(conn, columns, "asterisk_call_links", "priority", "INTEGER DEFAULT 3")
+            indexes = _table_indexes(inspector, "asterisk_call_links")
+            if "idx_asterisk_call_links_tenant_id" not in indexes:
+                conn.execute(
+                    text(
+                        "CREATE INDEX IF NOT EXISTS idx_asterisk_call_links_tenant_id "
+                        "ON asterisk_call_links(tenant_id)"
+                    )
+                )
+            if "idx_asterisk_call_links_current_level" not in indexes:
+                conn.execute(
+                    text(
+                        "CREATE INDEX IF NOT EXISTS idx_asterisk_call_links_current_level "
+                        "ON asterisk_call_links(current_level)"
+                    )
+                )
 
         if "voice_ai_sessions" in table_names:
             columns = _table_columns(inspector, "voice_ai_sessions")