Add PostgreSQL schema, seed data and documentation (#10)

docs/database.md

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+# Database – Spillkveld
+
+## Overview
+
+The project uses PostgreSQL to store board game data. The database schema and seed data are defined in two SQL files:
+
+- `server/db/schema.sql` – creates the `games` table and its constraints.
+- `server/db/seed.sql` – inserts the 12 example games from `src/data/games.ts`.
+
+The original game IDs and fields are preserved, including `icon` and `tone`.
+
+## Local setup
+
+PostgreSQL 17 was installed and tested locally on macOS using Homebrew.
+
+Install PostgreSQL:
+
+```bash
+brew install postgresql@17
+```
+
+Start the database service:
+
+```bash
+brew services start postgresql@17
+```
+
+Create a local database:
+
+```bash
+/opt/homebrew/opt/postgresql@17/bin/createdb spillkveld
+```
+
+Run the following commands from the project root:
+
+```bash
+/opt/homebrew/opt/postgresql@17/bin/psql -X -v ON_ERROR_STOP=1 -d spillkveld -f server/db/schema.sql
+/opt/homebrew/opt/postgresql@17/bin/psql -X -v ON_ERROR_STOP=1 -d spillkveld -f server/db/seed.sql
+```
+
+The PostgreSQL executable path shown above is specific to this local Homebrew installation. On other systems, the commands may use `psql` directly.
+
+## Database structure
+
+The `games` table contains the following fields:
+
+| Column | Type | Constraint |
+|---|---|---|
+| id | TEXT | PRIMARY KEY |
+| name | TEXT | NOT NULL |
+| description | TEXT | NOT NULL |
+| min_players | INTEGER | NOT NULL, >= 1 |
+| max_players | INTEGER | NOT NULL, >= min_players |
+| minutes | INTEGER | NOT NULL, > 0 |
+| category | TEXT | NOT NULL |
+| icon | TEXT | NOT NULL |
+| tone | TEXT | NOT NULL |
+
+## Seed data
+
+The seed file contains 12 example games based on the existing prototype data in `src/data/games.ts`.
+
+It uses `ON CONFLICT (id) DO NOTHING` to prevent duplicate rows when executed multiple times. Existing rows are left unchanged.
+
+## Local testing
+
+The following tests were completed using PostgreSQL 17.11:
+
+1. **Schema creation:** Executing `schema.sql` returned `CREATE TABLE`.
+2. **Seed insertion:** Executing `seed.sql` returned `INSERT 0 12`.
+3. **Repeated seed execution:** Running `seed.sql` again returned `INSERT 0 0`, confirming that no duplicate rows were inserted.
+4. **Row count:** `SELECT COUNT(*) FROM games;` returned 12.
+5. **Constraint validation:** An attempt to insert a game with `min_players = 0` was rejected by the `games_min_players_check` constraint.
+6. **Player range validation:** An attempt to insert a game with `min_players = 5` and `max_players = 2` was rejected by the `games_check` constraint, confirming that `max_players` cannot be lower than `min_players`.
+7. **Game duration validation:** An attempt to insert a game with `minutes = 0` was rejected by the `games_minutes_check` constraint.
+8. **NOT NULL validation:** An attempt to insert a game with `name = NULL` was rejected, confirming that the name field is required.
+
+The database schema and seed data were tested locally. Backend integration and deployment are handled separately.
+
+## AI usage
+
+ChatGPT was used to explain PostgreSQL setup, assist with drafting the SQL schema and seed file, and provide testing instructions. The SQL files were executed and their results verified locally.

server/db/schema.sql

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+CREATE TABLE IF NOT EXISTS games (
+    id TEXT PRIMARY KEY,
+    name TEXT NOT NULL,
+    description TEXT NOT NULL,
+    min_players INTEGER NOT NULL CHECK (min_players >= 1),
+    max_players INTEGER NOT NULL CHECK (max_players >= min_players),
+    minutes INTEGER NOT NULL CHECK (minutes > 0),
+    category TEXT NOT NULL,
+    icon TEXT NOT NULL,
+    tone TEXT NOT NULL
+);

server/db/seed.sql

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+
+-- Insert the 12 prototype games into the database.
+-- Keep the original IDs so the frontend and backend can reference them.
+-- ON CONFLICT prevents duplicate entries when the seed is run again.
+
+INSERT INTO games (
+    id,
+    name,
+    description,
+    min_players,
+    max_players,
+    minutes,
+    category,
+    icon,
+    tone
+)
+VALUES
+    ('azul', 'Azul',
+     'Legg fargerike fliser og bygg et mønster som gir flest poeng.',
+     2, 4, 40, 'Strategi', '▦', 'blue'),
+
+    ('codenames', 'Codenames',
+     'Gi smarte ledetråder og finn lagets hemmelige ord.',
+     2, 8, 20, 'Selskap', '✳', 'purple'),
+
+    ('carcassonne', 'Carcassonne',
+     'Bygg landskap med brikker og plasser følgere på byer og veier.',
+     2, 5, 45, 'Strategi', '⌂', 'green'),
+
+    ('dixit', 'Dixit',
+     'Fortell en liten historie til et bilde og gjett hvilket kort som er riktig.',
+     3, 6, 30, 'Kreativt', '✦', 'pink'),
+
+    ('ticket-to-ride', 'Ticket to Ride',
+     'Bygg togruter mellom byer og fullfør reisemålene dine.',
+     2, 5, 60, 'Familie', '↗', 'orange'),
+
+    ('pandemic', 'Pandemic',
+     'Samarbeid om å stoppe utbrudd før tiden renner ut.',
+     2, 4, 45, 'Samarbeid', '✚', 'teal'),
+
+    ('splendor', 'Splendor',
+     'Samle edelstener, kjøp kort og bygg en verdifull samling.',
+     2, 4, 30, 'Strategi', '◆', 'purple'),
+
+    ('just-one', 'Just One',
+     'Skriv ett hint hver og hjelp en spiller å gjette ordet.',
+     3, 7, 20, 'Samarbeid', '☝', 'yellow'),
+
+    ('kingdomino', 'Kingdomino',
+     'Velg dominobrikker og sett sammen ditt eget kongerike.',
+     2, 4, 25, 'Familie', '♛', 'green'),
+
+    ('7-wonders', '7 Wonders',
+     'Bygg en sivilisasjon med kort og samle ressurser over tre epoker.',
+     3, 7, 30, 'Strategi', '◭', 'orange'),
+
+    ('the-crew', 'The Crew',
+     'Løs oppdrag sammen ved å spille kort uten å si for mye.',
+     3, 5, 20, 'Samarbeid', '✧', 'blue'),
+
+    ('patchwork', 'Patchwork',
+     'Sy sammen et lappeteppe ved å velge og plassere brikker.',
+     2, 2, 30, 'Strategi', '▧', 'pink')
+
+ON CONFLICT (id) DO NOTHING;