Implement SQLite database persistence for instance management

pkg/database/migrations/001_initial_schema.down.sql

@@ -0,0 +1,7 @@
+-- Drop indexes first
+DROP INDEX IF EXISTS idx_instances_backend_type;
+DROP INDEX IF EXISTS idx_instances_status;
+DROP INDEX IF EXISTS idx_instances_name;
+
+-- Drop tables
+DROP TABLE IF EXISTS instances;

pkg/database/migrations/001_initial_schema.up.sql

@@ -0,0 +1,43 @@
+-- -----------------------------------------------------------------------------
+-- Instances Table: Central configuration and state for LLM backends
+-- -----------------------------------------------------------------------------
+CREATE TABLE IF NOT EXISTS instances (
+    -- Primary identification
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL UNIQUE,
+
+    -- Backend configuration
+    backend_type TEXT NOT NULL CHECK(backend_type IN ('llama_cpp', 'mlx_lm', 'vllm')),
+    backend_config_json TEXT NOT NULL, -- Backend-specific options (150+ fields for llama_cpp, etc.)
+
+    -- Instance state
+    status TEXT NOT NULL CHECK(status IN ('stopped', 'running', 'failed', 'restarting', 'shutting_down')) DEFAULT 'stopped',
+
+    -- Timestamps (created_at stored as Unix timestamp for compatibility with existing JSON format)
+    created_at INTEGER NOT NULL,
+    updated_at INTEGER NOT NULL,
+
+    -- Common instance options (extracted from Instance.Options)
+    -- NOT NULL with defaults to match config behavior (nil pointers use these defaults)
+    auto_restart INTEGER NOT NULL DEFAULT 0,        -- Boolean: Enable automatic restart on failure
+    max_restarts INTEGER NOT NULL DEFAULT -1,       -- Maximum restart attempts (-1 = unlimited)
+    restart_delay INTEGER NOT NULL DEFAULT 0,       -- Delay between restarts in seconds
+    on_demand_start INTEGER NOT NULL DEFAULT 0,     -- Boolean: Enable on-demand instance start
+    idle_timeout INTEGER NOT NULL DEFAULT 0,        -- Idle timeout in minutes before auto-stop
+    docker_enabled INTEGER NOT NULL DEFAULT 0,      -- Boolean: Run instance in Docker container
+    command_override TEXT,                          -- Custom command to override default backend command (nullable)
+
+    -- JSON fields for complex structures (nullable - empty when not set)
+    nodes TEXT,                            -- JSON array of node names for remote instances
+    environment TEXT,                      -- JSON map of environment variables
+
+    -- Future extensibility hook
+    owner_user_id TEXT NULL                -- Future: OIDC user ID for ownership
+);
+
+-- -----------------------------------------------------------------------------
+-- Indexes for performance
+-- -----------------------------------------------------------------------------
+CREATE UNIQUE INDEX IF NOT EXISTS idx_instances_name ON instances(name);
+CREATE INDEX IF NOT EXISTS idx_instances_status ON instances(status);
+CREATE INDEX IF NOT EXISTS idx_instances_backend_type ON instances(backend_type);