Implement local DB migrations and archived configuration lifecycle

migrations/006_add_local_configuration_versions.sql

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+-- Add full-snapshot versioning for local configurations (SQLite)
+-- 1) Create local_configuration_versions
+-- 2) Add current_version_id to local_configurations
+-- 3) Backfill v1 snapshots from existing local_configurations
+
+PRAGMA foreign_keys = ON;
+
+BEGIN TRANSACTION;
+
+CREATE TABLE local_configuration_versions (
+    id TEXT PRIMARY KEY,
+    configuration_uuid TEXT NOT NULL,
+    version_no INTEGER NOT NULL,
+    data TEXT NOT NULL,
+    change_note TEXT NULL,
+    created_by TEXT NULL,
+    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (configuration_uuid) REFERENCES local_configurations(uuid),
+    UNIQUE(configuration_uuid, version_no)
+);
+
+ALTER TABLE local_configurations
+    ADD COLUMN current_version_id TEXT NULL;
+
+CREATE INDEX idx_lcv_config_created
+    ON local_configuration_versions(configuration_uuid, created_at DESC);
+
+CREATE INDEX idx_lcv_config_version
+    ON local_configuration_versions(configuration_uuid, version_no DESC);
+
+-- Backfill v1 snapshot for every existing configuration.
+INSERT INTO local_configuration_versions (
+    id,
+    configuration_uuid,
+    version_no,
+    data,
+    change_note,
+    created_by,
+    created_at
+)
+SELECT
+    uuid || '-v1' AS id,
+    uuid AS configuration_uuid,
+    1 AS version_no,
+    json_object(
+        'uuid', uuid,
+        'server_id', server_id,
+        'name', name,
+        'items', CASE WHEN json_valid(items) THEN json(items) ELSE items END,
+        'total_price', total_price,
+        'custom_price', custom_price,
+        'notes', notes,
+        'is_template', is_template,
+        'server_count', server_count,
+        'price_updated_at', price_updated_at,
+        'created_at', created_at,
+        'updated_at', updated_at,
+        'synced_at', synced_at,
+        'sync_status', sync_status,
+        'original_user_id', original_user_id,
+        'original_username', original_username
+    ) AS data,
+    'Initial snapshot backfill (v1)' AS change_note,
+    NULL AS created_by,
+    COALESCE(created_at, CURRENT_TIMESTAMP) AS created_at
+FROM local_configurations;
+
+UPDATE local_configurations
+SET current_version_id = (
+    SELECT lcv.id
+    FROM local_configuration_versions lcv
+    WHERE lcv.configuration_uuid = local_configurations.uuid
+      AND lcv.version_no = 1
+);
+
+COMMIT;