feat: add bump-version.sh script for version management

Automates version bumps across all version source files:
- Cargo.toml (PRIMARY - workspace.package.version)
- debian/changelog (prepend new entry)
- debian/control (update Version field)
- scripts/build-package.sh (update VERSION variable)
- frontend/package.json (update version field)
- Stale references check after bump

Usage: ./scripts/bump-version.sh <new_version> <old_version>

migrations/003_jobs_scheduling.sql

@@ -0,0 +1,44 @@
+-- Migration: 003_jobs_scheduling
+-- Description: Retry/scheduling columns for patch_job_hosts, and NOTIFY trigger
+--              for immediate patch job dispatch.
+
+-- ============================================================
+-- Add retry-scheduling columns to patch_job_hosts
+-- ============================================================
+
+-- When the retry engine should next attempt this host; NULL = not scheduled
+ALTER TABLE patch_job_hosts
+    ADD COLUMN retry_next_at TIMESTAMPTZ;
+
+-- Last failure reason captured by the worker for display in the UI
+ALTER TABLE patch_job_hosts
+    ADD COLUMN last_error TEXT;
+
+-- ============================================================
+-- pg_notify trigger: fires when an immediate job is inserted
+-- ============================================================
+
+CREATE OR REPLACE FUNCTION notify_job_enqueued()
+    RETURNS TRIGGER
+    LANGUAGE plpgsql
+AS $$
+BEGIN
+    IF NEW.immediate = TRUE THEN
+        PERFORM pg_notify('job_enqueued', NEW.id::text);
+    END IF;
+    RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER trg_job_enqueued
+    AFTER INSERT ON patch_jobs
+    FOR EACH ROW
+    EXECUTE FUNCTION notify_job_enqueued();
+
+-- ============================================================
+-- Index: efficiently find hosts due for retry
+-- ============================================================
+
+CREATE INDEX idx_pjh_retry
+    ON patch_job_hosts (retry_next_at)
+    WHERE retry_next_at IS NOT NULL;