feat: implement filament and spool preset services with CRUD operations

- Add `FilamentService` for managing filament inventory, including creation, retrieval, updating, and deletion of filaments.
- Introduce `SpoolPresetService` for handling spool presets, allowing users to create, update, and delete their custom presets.
- Create domain models for `Filament` and `SpoolPreset` with necessary fields and methods.
- Define repository interfaces for filament and spool preset persistence.
- Implement application configuration management from environment variables.
- Set up error handling with a centralized `AppError` type.
- Build the Axum router with public and protected routes for user authentication and resource management.

backend/migrations/20240101000002_create_spool_presets.sql

@@ -0,0 +1,30 @@
+-- Migration: 002 - Criar tabela de presets de carretel e inserir presets do sistema
+
+CREATE TABLE spool_presets (
+    id              UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    name            TEXT NOT NULL,
+    spool_weight_g  INTEGER NOT NULL CHECK (spool_weight_g > 0),
+    is_system       BOOLEAN NOT NULL DEFAULT FALSE,
+    user_id         UUID REFERENCES users (id) ON DELETE CASCADE,
+    created_at      TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+
+    -- Presets do sistema não têm user_id; presets customizados têm
+    CONSTRAINT chk_preset_ownership CHECK (
+        (is_system = TRUE AND user_id IS NULL) OR
+        (is_system = FALSE AND user_id IS NOT NULL)
+    )
+);
+
+CREATE INDEX idx_spool_presets_user_id  ON spool_presets (user_id) WHERE user_id IS NOT NULL;
+CREATE INDEX idx_spool_presets_is_system ON spool_presets (is_system);
+
+-- Presets built-in do sistema (somente leitura para usuários)
+INSERT INTO spool_presets (name, spool_weight_g, is_system) VALUES
+    ('Bambu Lab (Plástico)',   250, TRUE),
+    ('Elegoo (Papelão)',       200, TRUE),
+    ('Creality (Plástico)',    230, TRUE),
+    ('Prusament (Plástico)',   201, TRUE),
+    ('Sunlu (Papelão)',        200, TRUE),
+    ('Polymaker (Plástico)',   220, TRUE),
+    ('Genérico Papelão 1kg',   200, TRUE),
+    ('Genérico Plástico 1kg',  250, TRUE);