Add search/metadata API endpoint

- Add MetadataSearchRequest, SearchResponse, SearchAssetResult,
  SearchAlbumResult, SearchFacet, SearchFacetCount models
- Create SearchApi with SearchMetadataBuilder supporting 35+ filters
- Support filtering by location, dates, camera info, favorites,
  tags, people, albums, text search, and more
- Integrate into Client with client.search().metadata() API

src/models/mod.rs

@@ -344,6 +344,180 @@ pub struct TimeBucketAssetResponse {
     pub visibility: Vec<AssetVisibility>,
 }
 
+/// Metadata search request for filtering assets
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+#[serde(rename_all = "camelCase")]
+pub struct MetadataSearchRequest {
+    /// Filter by album IDs
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub album_ids: Option<Vec<AssetId>>,
+    /// Filter by file checksum
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub checksum: Option<String>,
+    /// Filter by city name
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub city: Option<String>,
+    /// Filter by country name
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub country: Option<String>,
+    /// Filter by creation date (after)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub created_after: Option<DateTime<Utc>>,
+    /// Filter by creation date (before)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub created_before: Option<DateTime<Utc>>,
+    /// Filter by description text
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub description: Option<String>,
+    /// Filter by device asset ID
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub device_asset_id: Option<String>,
+    /// Device ID to filter by
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub device_id: Option<String>,
+    /// Filter by favorite status
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub is_favorite: Option<bool>,
+    /// Filter by motion photo status
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub is_motion: Option<bool>,
+    /// Filter assets not in any album
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub is_not_in_album: Option<bool>,
+    /// Filter by offline status
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub is_offline: Option<bool>,
+    /// Filter by lens model
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub lens_model: Option<String>,
+    /// Library ID to filter by
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub library_id: Option<AssetId>,
+    /// Filter by camera make
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub make: Option<String>,
+    /// Filter by camera model
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub model: Option<String>,
+    /// Filter by OCR text content
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub ocr: Option<String>,
+    /// Sort order
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub order: Option<AssetOrder>,
+    /// Filter by original file name
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub original_file_name: Option<String>,
+    /// Page number (default: 1)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub page: Option<u32>,
+    /// Filter by person IDs
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub person_ids: Option<Vec<AssetId>>,
+    /// Filter by rating [1-5], or null for unrated (-1 deprecated)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub rating: Option<i32>,
+    /// Number of results to return (default: 100)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub size: Option<u32>,
+    /// Filter by state/province name
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub state: Option<String>,
+    /// Filter by tag IDs
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub tag_ids: Option<Vec<AssetId>>,
+    /// Filter by taken date (after)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub taken_after: Option<DateTime<Utc>>,
+    /// Filter by taken date (before)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub taken_before: Option<DateTime<Utc>>,
+    /// Asset type filter
+    #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
+    pub asset_type: Option<AssetType>,
+    /// Filter by update date (after)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub updated_after: Option<DateTime<Utc>>,
+    /// Filter by update date (before)
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub updated_before: Option<DateTime<Utc>>,
+    /// Filter by visibility
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub visibility: Option<AssetVisibility>,
+    /// Include deleted assets
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub with_deleted: Option<bool>,
+    /// Include EXIF data in response
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub with_exif: Option<bool>,
+    /// Include people data in response
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub with_people: Option<bool>,
+    /// Include stacked assets
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub with_stacked: Option<bool>,
+}
+
+/// Represents a facet value count
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchFacetCount {
+    /// Number of assets with this facet value
+    pub count: i64,
+    /// Facet value
+    pub value: String,
+}
+
+/// Represents a search facet
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchFacet {
+    /// Facet counts
+    pub counts: Vec<SearchFacetCount>,
+    /// Facet field name
+    pub field_name: String,
+}
+
+/// Paginated asset search results
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchAssetResult {
+    /// Number of assets in this page
+    pub count: i64,
+    /// Facet information
+    pub facets: Vec<SearchFacet>,
+    /// The actual assets
+    pub items: Vec<AssetResponse>,
+    /// Next page token
+    pub next_page: Option<String>,
+    /// Total number of matching assets
+    pub total: i64,
+}
+
+/// Paginated album search results
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchAlbumResult {
+    /// Number of albums in this page
+    pub count: i64,
+    /// Facet information
+    pub facets: Vec<SearchFacet>,
+    /// The actual albums
+    pub items: Vec<AlbumResponse>,
+    /// Total number of matching albums
+    pub total: i64,
+}
+
+/// Combined search response
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SearchResponse {
+    /// Album results
+    pub albums: SearchAlbumResult,
+    /// Asset results
+    pub assets: SearchAssetResult,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;