Add asset metadata, sharing, and MinIO-backed signed links.

This introduces deduplicated per-user image/3D asset records linked into feature properties, adds visibility-controlled download routing, and wires local S3-compatible storage with automatic bucket bootstrap in Docker Compose.

Made-with: Cursor

internal/store/migrations/0002_assets.sql

@@ -0,0 +1,28 @@
+CREATE TABLE IF NOT EXISTS assets (
+  id TEXT PRIMARY KEY,
+  owner_key TEXT NOT NULL,
+  checksum TEXT NOT NULL,
+  ext TEXT NOT NULL,
+  kind TEXT NOT NULL,
+  mime_type TEXT,
+  size_bytes BIGINT NOT NULL DEFAULT 0,
+  object_key TEXT NOT NULL,
+  is_public BOOLEAN NOT NULL DEFAULT TRUE,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  UNIQUE (owner_key, checksum, ext),
+  UNIQUE (owner_key, object_key)
+);
+
+CREATE TABLE IF NOT EXISTS feature_asset_links (
+  feature_id TEXT NOT NULL REFERENCES features(id) ON DELETE CASCADE,
+  asset_id TEXT NOT NULL REFERENCES assets(id) ON DELETE CASCADE,
+  name TEXT,
+  description TEXT,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  PRIMARY KEY (feature_id, asset_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_assets_owner ON assets(owner_key);
+CREATE INDEX IF NOT EXISTS idx_assets_owner_public ON assets(owner_key, is_public);
+CREATE INDEX IF NOT EXISTS idx_feature_asset_links_asset ON feature_asset_links(asset_id);