feat(db): add saved_filters table and CRUD operations

Add database schema and SQL queries for generic saved filters system
that allows users to save custom filter presets for any resource type.

Database Schema:
- Add saved_filters table with user_id, name, resource_type, filters (JSONB)
- Create composite index on (user_id, resource_type) for efficient lookups
- Create index on (user_id, name) for future name search feature
- Add update_updated_at_column() trigger to auto-update timestamps
- Make trigger creation idempotent with DROP TRIGGER IF EXISTS

SQL Queries (5 new queries):
- GetSavedFilters: List all filters for user + resource type
- GetSavedFilterByID: Retrieve single filter by ID
- CreateSavedFilter: Create new saved filter
- UpdateSavedFilter: Update filter name/criteria
- DeleteSavedFilter: Remove saved filter

Design Decisions:
- Generic resource_type field supports any resource (media-items, collections, devices)
- JSONB filters field allows flexible schema without migrations
- User-scoped via JWT (user_id foreign key with CASCADE delete)
- Automatic updated_at timestamp via database trigger

Generated Code:
- database.SavedFilters model (10 fields including JSONB filters)
- All 5 CRUD query functions with proper parameter types
- pgtype.UUID wrappers for UUID parameters

Part of: Saved Filters Implementation (Phase 1: Database)
Related: #saved-filters-feature

internal/database/queries/queries.sql

@@ -1721,3 +1721,29 @@ LIMIT $3;
 SELECT mi.* FROM media_items mi
 WHERE mi.library_id = $1
 ORDER BY mi.created_at DESC;
+
+-- name: GetSavedFilters :many
+SELECT * FROM saved_filters
+WHERE user_id = @user_id AND resource_type = @resource_type
+ORDER BY created_at DESC;
+
+-- name: GetSavedFilterByID :one
+SELECT * FROM saved_filters
+WHERE id = @id AND user_id = @user_id;
+
+-- name: CreateSavedFilter :one
+INSERT INTO saved_filters (user_id, name, resource_type, filters)
+VALUES (@user_id, @name, @resource_type, @filters)
+RETURNING *;
+
+-- name: UpdateSavedFilter :one
+UPDATE saved_filters
+SET name = @name,
+    filters = @filters,
+    updated_at = NOW()
+WHERE id = @id AND user_id = @user_id
+RETURNING *;
+
+-- name: DeleteSavedFilter :exec
+DELETE FROM saved_filters
+WHERE id = @id AND user_id = @user_id;