refactor(db): port metrics storage + service domains to sqlc

First tranche of the ~300-site raw SQL port. Metrics: node/service/
instance rows via generated queries; aggregation moved off TimescaleDB's
time_bucket onto portable date_bin (PG14+); interval uptime returns epoch
seconds; per-container writes dropped (container_metrics FKs a different
model — collector shape never matched). Domains: all reads/writes through
sqlcdb including the create transaction via WithTx; default-domain and
services.domain invariants unchanged. Both paths covered by live
Postgres tests gated on METRICS_TEST_DSN.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/sqlc/schema.sql

@@ -346,3 +346,90 @@ CREATE TABLE notification_channels (
     created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
     updated_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
 );
+
+CREATE TABLE node_metrics (
+    node_id VARCHAR(255) NOT NULL,
+    timestamp TIMESTAMP WITH TIME ZONE NOT NULL,
+    cpu_usage NUMERIC(5,2),
+    cpu_cores NUMERIC(10,2),
+    load_avg_1 NUMERIC(5,2),
+    load_avg_5 NUMERIC(5,2),
+    load_avg_15 NUMERIC(5,2),
+    memory_total BIGINT,
+    memory_used BIGINT,
+    memory_available BIGINT,
+    memory_usage_percent NUMERIC(5,2),
+    storage_total BIGINT,
+    storage_used BIGINT,
+    storage_available BIGINT,
+    storage_usage_percent NUMERIC(5,2),
+    network_bytes_in BIGINT,
+    network_bytes_out BIGINT,
+    network_packets_in BIGINT,
+    network_packets_out BIGINT,
+    network_connections_in INTEGER,
+    network_connections_out INTEGER,
+    network_errors_in BIGINT,
+    network_errors_out BIGINT,
+    uptime INTERVAL,
+    processes INTEGER,
+    os VARCHAR(50),
+    kernel VARCHAR(50),
+    architecture VARCHAR(20),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    PRIMARY KEY (node_id, timestamp)
+);
+
+CREATE TABLE service_metrics (
+    service_id VARCHAR(255) NOT NULL,
+    service_name VARCHAR(255) NOT NULL,
+    project_id VARCHAR(255) NOT NULL,
+    timestamp TIMESTAMP WITH TIME ZONE NOT NULL,
+    requests_total BIGINT DEFAULT 0,
+    requests_success BIGINT DEFAULT 0,
+    requests_errors BIGINT DEFAULT 0,
+    requests_avg_latency NUMERIC(10,3),
+    requests_p95_latency NUMERIC(10,3),
+    requests_p99_latency NUMERIC(10,3),
+    requests_throughput NUMERIC(10,3),
+    errors_total BIGINT DEFAULT 0,
+    errors_rate NUMERIC(5,4),
+    performance_response_time NUMERIC(10,3),
+    performance_throughput NUMERIC(10,3),
+    performance_concurrency BIGINT,
+    performance_saturation NUMERIC(5,2),
+    performance_utilization NUMERIC(5,2),
+    resource_cpu_usage NUMERIC(5,2),
+    resource_memory_usage BIGINT,
+    resource_storage_usage BIGINT,
+    resource_network_usage BIGINT,
+    resource_score NUMERIC(5,2),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    PRIMARY KEY (service_id, timestamp)
+);
+
+CREATE TABLE instance_metrics (
+    service_id VARCHAR(255) NOT NULL,
+    timestamp TIMESTAMP WITH TIME ZONE NOT NULL,
+    instance_id VARCHAR(255) NOT NULL,
+    node_id VARCHAR(255),
+    status VARCHAR(50),
+    cpu NUMERIC(5,2),
+    memory BIGINT,
+    network_bytes_in BIGINT,
+    network_bytes_out BIGINT,
+    network_packets_in BIGINT,
+    network_packets_out BIGINT,
+    network_connections_in INTEGER,
+    network_connections_out INTEGER,
+    network_errors_in BIGINT,
+    network_errors_out BIGINT,
+    start_time TIMESTAMP WITH TIME ZONE,
+    last_seen TIMESTAMP WITH TIME ZONE,
+    health_status VARCHAR(20),
+    health_last_check TIMESTAMP WITH TIME ZONE,
+    health_check_count INTEGER DEFAULT 0,
+    health_failure_count INTEGER DEFAULT 0,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    PRIMARY KEY (service_id, timestamp, instance_id)
+);