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

database/schema/schema.sql

@@ -992,3 +992,36 @@ CREATE TABLE IF NOT EXISTS unlinked_books (
 CREATE INDEX IF NOT EXISTS idx_unlinked_books_device ON unlinked_books(device_id);
 CREATE INDEX IF NOT EXISTS idx_unlinked_books_content_id ON unlinked_books(content_id);
 CREATE INDEX IF NOT EXISTS idx_unlinked_books_resolved ON unlinked_books(resolved);
+
+-- Create saved_filters for users to be able to filter different parts of the application
+CREATE TABLE IF NOT EXISTS saved_filters (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    name TEXT NOT NULL,
+    resource_type TEXT NOT NULL, -- 'media-items', 'collections', 'devices', etc.
+    filters JSONB NOT NULL, -- {search: "", author_filter: "", genre: "", ...}
+    created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+-- Index for efficient user+resource lookups
+CREATE INDEX IF NOT EXISTS idx_saved_filters_user_resource ON saved_filters(user_id, resource_type);
+
+-- Index for name searches (future feature)
+CREATE INDEX IF NOT EXISTS idx_saved_filters_name ON saved_filters(user_id, name);
+
+-- Trigger to auto-update updated_at timestamp
+CREATE OR REPLACE FUNCTION update_updated_at_column()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = NOW();
+    RETURN NEW;
+END;
+$$ language 'plpgsql';
+
+DROP TRIGGER IF EXISTS update_saved_filters_updated_at ON saved_filters;
+
+CREATE TRIGGER update_saved_filters_updated_at
+    BEFORE UPDATE ON saved_filters
+    FOR EACH ROW
+    EXECUTE FUNCTION update_updated_at_column();