feat: add Sense identity RBAC and audit (#22)

Sense/server/database/migrations/sense_identity/2026081201_identity.sql

@@ -0,0 +1,27 @@
+CREATE TABLE IF NOT EXISTS sense_identity_users (
+    id TEXT PRIMARY KEY,
+    username TEXT NOT NULL UNIQUE,
+    display_name TEXT NOT NULL,
+    role TEXT NOT NULL,
+    enabled BOOLEAN NOT NULL DEFAULT TRUE,
+    password_hash TEXT NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL,
+    updated_at TIMESTAMPTZ NOT NULL
+);
+CREATE TABLE IF NOT EXISTS sense_identity_sessions (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL REFERENCES sense_identity_users(id),
+    expires_at TIMESTAMPTZ NOT NULL,
+    revoked_at TIMESTAMPTZ NULL
+);
+CREATE TABLE IF NOT EXISTS sense_identity_audit (
+    id TEXT PRIMARY KEY,
+    actor_id TEXT NULL REFERENCES sense_identity_users(id),
+    action TEXT NOT NULL,
+    target TEXT NOT NULL DEFAULT '',
+    outcome TEXT NOT NULL,
+    metadata JSONB NOT NULL DEFAULT '{}'::jsonb,
+    created_at TIMESTAMPTZ NOT NULL
+);
+CREATE INDEX IF NOT EXISTS sense_identity_audit_created_idx ON sense_identity_audit(created_at DESC);
+