Add initial MySQL schema, gitignore, and improved README

- db.sql: tables for printers, filaments, print_jobs, todos, pricing_config
- .gitignore: excludes .env files and Python build artefacts
- README: cleaned up structure and added Getting Started section

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

db.sql

@@ -0,0 +1,84 @@
+-- POPS — Printing Operations Production System
+-- Initial schema
+
+CREATE DATABASE IF NOT EXISTS pops CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+USE pops;
+
+-- ─── Printers ────────────────────────────────────────────────────────────────
+
+CREATE TABLE printers (
+    id          INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    name        VARCHAR(100) NOT NULL,
+    model       VARCHAR(100),
+    location    VARCHAR(100),
+    status      ENUM('idle', 'printing', 'error', 'offline') NOT NULL DEFAULT 'offline',
+    created_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+);
+
+-- ─── Filaments ───────────────────────────────────────────────────────────────
+
+CREATE TABLE filaments (
+    id                  INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    brand               VARCHAR(100),
+    material            ENUM('PLA', 'PETG', 'ABS', 'ASA', 'TPU', 'Nylon', 'PC', 'Other') NOT NULL DEFAULT 'PLA',
+    color               VARCHAR(100),
+    color_hex           CHAR(7),                    -- e.g. #FF5733
+    weight_total_g      DECIMAL(8,2) NOT NULL,      -- spool size in grams
+    weight_remaining_g  DECIMAL(8,2) NOT NULL,
+    price_per_kg_eur    DECIMAL(8,2),
+    created_at          DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at          DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+);
+
+-- ─── Print jobs ──────────────────────────────────────────────────────────────
+
+CREATE TABLE print_jobs (
+    id                  INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    printer_id          INT UNSIGNED NOT NULL,
+    filament_id         INT UNSIGNED,
+    name                VARCHAR(200) NOT NULL,
+    file_name           VARCHAR(255),
+    status              ENUM('queued', 'printing', 'done', 'failed', 'cancelled') NOT NULL DEFAULT 'queued',
+    queue_position      INT UNSIGNED,               -- NULL when not queued
+    started_at          DATETIME,
+    finished_at         DATETIME,
+    duration_minutes    INT UNSIGNED,
+    filament_used_g     DECIMAL(8,2),
+    cost_eur            DECIMAL(8,2),               -- calculated at job completion
+    notes               TEXT,
+    created_at          DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at          DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+
+    CONSTRAINT fk_job_printer  FOREIGN KEY (printer_id)  REFERENCES printers(id),
+    CONSTRAINT fk_job_filament FOREIGN KEY (filament_id) REFERENCES filaments(id)
+);
+
+-- ─── To-do list ──────────────────────────────────────────────────────────────
+
+CREATE TABLE todos (
+    id          INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    title       VARCHAR(255) NOT NULL,
+    done        BOOLEAN NOT NULL DEFAULT FALSE,
+    printer_id  INT UNSIGNED,                       -- optional: linked to a specific printer
+    created_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at  DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+
+    CONSTRAINT fk_todo_printer FOREIGN KEY (printer_id) REFERENCES printers(id)
+);
+
+-- ─── Pricing configuration ───────────────────────────────────────────────────
+
+CREATE TABLE pricing_config (
+    id                      INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    name                    VARCHAR(100) NOT NULL DEFAULT 'default',
+    electricity_kwh_eur     DECIMAL(6,4) NOT NULL DEFAULT 0.30,
+    printer_watt            DECIMAL(8,2) NOT NULL DEFAULT 200.00,  -- average power draw
+    hourly_rate_eur         DECIMAL(8,2) NOT NULL DEFAULT 0.00,    -- operator cost per hour
+    markup_percent          DECIMAL(5,2) NOT NULL DEFAULT 20.00,
+    valid_from              DATE NOT NULL DEFAULT (CURRENT_DATE),
+    created_at              DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Seed a default pricing row
+INSERT INTO pricing_config (name) VALUES ('default');