merge: 合并main分支最新改动

解决冲突：
- backend/internal/config/config.go: 合并Ops和Dashboard配置
- backend/internal/server/api_contract_test.go: 合并handler初始化
- backend/internal/service/openai_gateway_service.go: 保留Ops错误追踪逻辑
- backend/internal/service/wire.go: 合并Ops和APIKeyAuth provider

主要合并内容：
- Dashboard缓存和预聚合功能
- API Key认证缓存优化
- Codex转换支持
- 使用日志分区表

backend/migrations/034_usage_dashboard_aggregation_tables.sql

@@ -0,0 +1,77 @@
+-- Usage dashboard aggregation tables (hourly/daily) + active-user dedup + watermark.
+-- These tables support Admin Dashboard statistics without full-table scans on usage_logs.
+
+-- Hourly aggregates (UTC buckets).
+CREATE TABLE IF NOT EXISTS usage_dashboard_hourly (
+    bucket_start TIMESTAMPTZ PRIMARY KEY,
+    total_requests BIGINT NOT NULL DEFAULT 0,
+    input_tokens BIGINT NOT NULL DEFAULT 0,
+    output_tokens BIGINT NOT NULL DEFAULT 0,
+    cache_creation_tokens BIGINT NOT NULL DEFAULT 0,
+    cache_read_tokens BIGINT NOT NULL DEFAULT 0,
+    total_cost DECIMAL(20, 10) NOT NULL DEFAULT 0,
+    actual_cost DECIMAL(20, 10) NOT NULL DEFAULT 0,
+    total_duration_ms BIGINT NOT NULL DEFAULT 0,
+    active_users BIGINT NOT NULL DEFAULT 0,
+    computed_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_usage_dashboard_hourly_bucket_start
+    ON usage_dashboard_hourly (bucket_start DESC);
+
+COMMENT ON TABLE usage_dashboard_hourly IS 'Pre-aggregated hourly usage metrics for admin dashboard (UTC buckets).';
+COMMENT ON COLUMN usage_dashboard_hourly.bucket_start IS 'UTC start timestamp of the hour bucket.';
+COMMENT ON COLUMN usage_dashboard_hourly.computed_at IS 'When the hourly row was last computed/refreshed.';
+
+-- Daily aggregates (UTC dates).
+CREATE TABLE IF NOT EXISTS usage_dashboard_daily (
+    bucket_date DATE PRIMARY KEY,
+    total_requests BIGINT NOT NULL DEFAULT 0,
+    input_tokens BIGINT NOT NULL DEFAULT 0,
+    output_tokens BIGINT NOT NULL DEFAULT 0,
+    cache_creation_tokens BIGINT NOT NULL DEFAULT 0,
+    cache_read_tokens BIGINT NOT NULL DEFAULT 0,
+    total_cost DECIMAL(20, 10) NOT NULL DEFAULT 0,
+    actual_cost DECIMAL(20, 10) NOT NULL DEFAULT 0,
+    total_duration_ms BIGINT NOT NULL DEFAULT 0,
+    active_users BIGINT NOT NULL DEFAULT 0,
+    computed_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_usage_dashboard_daily_bucket_date
+    ON usage_dashboard_daily (bucket_date DESC);
+
+COMMENT ON TABLE usage_dashboard_daily IS 'Pre-aggregated daily usage metrics for admin dashboard (UTC dates).';
+COMMENT ON COLUMN usage_dashboard_daily.bucket_date IS 'UTC date of the day bucket.';
+COMMENT ON COLUMN usage_dashboard_daily.computed_at IS 'When the daily row was last computed/refreshed.';
+
+-- Hourly active user dedup table.
+CREATE TABLE IF NOT EXISTS usage_dashboard_hourly_users (
+    bucket_start TIMESTAMPTZ NOT NULL,
+    user_id BIGINT NOT NULL,
+    PRIMARY KEY (bucket_start, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_usage_dashboard_hourly_users_bucket_start
+    ON usage_dashboard_hourly_users (bucket_start);
+
+-- Daily active user dedup table.
+CREATE TABLE IF NOT EXISTS usage_dashboard_daily_users (
+    bucket_date DATE NOT NULL,
+    user_id BIGINT NOT NULL,
+    PRIMARY KEY (bucket_date, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_usage_dashboard_daily_users_bucket_date
+    ON usage_dashboard_daily_users (bucket_date);
+
+-- Aggregation watermark table (single row).
+CREATE TABLE IF NOT EXISTS usage_dashboard_aggregation_watermark (
+    id INT PRIMARY KEY,
+    last_aggregated_at TIMESTAMPTZ NOT NULL DEFAULT TIMESTAMPTZ '1970-01-01 00:00:00+00',
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+INSERT INTO usage_dashboard_aggregation_watermark (id)
+VALUES (1)
+ON CONFLICT (id) DO NOTHING;

backend/migrations/035_usage_logs_partitioning.sql

@@ -0,0 +1,54 @@
+-- usage_logs monthly partition bootstrap.
+-- Only creates partitions when usage_logs is already partitioned.
+-- Converting usage_logs to a partitioned table requires a manual migration plan.
+
+DO $$
+DECLARE
+    is_partitioned BOOLEAN := FALSE;
+    has_data BOOLEAN := FALSE;
+    month_start DATE;
+    prev_month DATE;
+    next_month DATE;
+BEGIN
+    SELECT EXISTS(
+        SELECT 1
+        FROM pg_partitioned_table pt
+        JOIN pg_class c ON c.oid = pt.partrelid
+        WHERE c.relname = 'usage_logs'
+    ) INTO is_partitioned;
+
+    IF NOT is_partitioned THEN
+        SELECT EXISTS(SELECT 1 FROM usage_logs LIMIT 1) INTO has_data;
+        IF NOT has_data THEN
+            -- Automatic conversion is intentionally skipped; see manual migration plan.
+            RAISE NOTICE 'usage_logs is not partitioned; skip automatic partitioning';
+        END IF;
+    END IF;
+
+    IF is_partitioned THEN
+        month_start := date_trunc('month', now() AT TIME ZONE 'UTC')::date;
+        prev_month := (month_start - INTERVAL '1 month')::date;
+        next_month := (month_start + INTERVAL '1 month')::date;
+
+        EXECUTE format(
+            'CREATE TABLE IF NOT EXISTS usage_logs_%s PARTITION OF usage_logs FOR VALUES FROM (%L) TO (%L)',
+            to_char(prev_month, 'YYYYMM'),
+            prev_month,
+            month_start
+        );
+
+        EXECUTE format(
+            'CREATE TABLE IF NOT EXISTS usage_logs_%s PARTITION OF usage_logs FOR VALUES FROM (%L) TO (%L)',
+            to_char(month_start, 'YYYYMM'),
+            month_start,
+            next_month
+        );
+
+        EXECUTE format(
+            'CREATE TABLE IF NOT EXISTS usage_logs_%s PARTITION OF usage_logs FOR VALUES FROM (%L) TO (%L)',
+            to_char(next_month, 'YYYYMM'),
+            next_month,
+            (next_month + INTERVAL '1 month')::date
+        );
+    END IF;
+END $$;