Feat: add POSIX DB projection

Backend/db/migrations/000004_posix_nodes.sql

@@ -0,0 +1,45 @@
+-- +goose Up
+
+CREATE TYPE posix_node_kind AS ENUM ('directory', 'file');
+
+CREATE TABLE IF NOT EXISTS posix_nodes (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  path TEXT NOT NULL UNIQUE,
+  parent_path TEXT,
+  name TEXT NOT NULL,
+  depth INTEGER NOT NULL,
+  node_kind posix_node_kind NOT NULL,
+  logical_type TEXT NOT NULL DEFAULT 'generic',
+  file_role TEXT,
+  resource_id TEXT,
+  resource_name TEXT,
+  resource_slug TEXT,
+  installation_id TEXT,
+  organization_id TEXT,
+  organization_slug TEXT,
+  department_slug TEXT,
+  team_slug TEXT,
+  project_slug TEXT,
+  personal_slug TEXT,
+  content_json JSONB,
+  size_bytes BIGINT NOT NULL DEFAULT 0,
+  checksum TEXT,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_posix_nodes_parent_path ON posix_nodes (parent_path);
+CREATE INDEX IF NOT EXISTS idx_posix_nodes_logical_type ON posix_nodes (logical_type);
+CREATE INDEX IF NOT EXISTS idx_posix_nodes_project_slug ON posix_nodes (project_slug);
+CREATE INDEX IF NOT EXISTS idx_posix_nodes_department_slug ON posix_nodes (department_slug);
+CREATE INDEX IF NOT EXISTS idx_posix_nodes_team_slug ON posix_nodes (team_slug);
+
+-- +goose Down
+
+DROP INDEX IF EXISTS idx_posix_nodes_team_slug;
+DROP INDEX IF EXISTS idx_posix_nodes_department_slug;
+DROP INDEX IF EXISTS idx_posix_nodes_project_slug;
+DROP INDEX IF EXISTS idx_posix_nodes_logical_type;
+DROP INDEX IF EXISTS idx_posix_nodes_parent_path;
+DROP TABLE IF EXISTS posix_nodes;
+DROP TYPE IF EXISTS posix_node_kind;