Fix "under" date semantics in oracle queries and add --all to generation scripts

Q80 and Q107 incorrectly used date ranges meaning "before year X" instead
of "during year X" (Swedish "under"). Changed to use YEAR() consistently.
Q106 also migrated from date range to YEAR() for consistency. Removed
legacy extract-oracle.ts, added --all flag to generate-language.ts and
generate-erd.ts, simplified generate-all script, and updated README with
architecture docs.

Author: Edwinexd

README.md

@@ -10,17 +10,55 @@ SQL Validator is a fully client-side web application powered by sql.js. Designed
 - **Question Highlighting**: Started and completed questions are highlighted in the question selector making it easy to track progress.
 - **Import/Export Data**: Import and export queries and views to file for sharing and/or backups.
 - **Image Export**: Export queries and views as images in light mode for assignment submission.
+- **Multi-Language Support**: Full i18n support with Swedish and English included. Adding a new language only requires a new language pack file.
 
 ## Usage
 ### Public Deployment
 A public instance of SQL Validator is available at [https://sql-validator.e-su.se](https://sql-validator.e-su.se), powered with Cloudflare Pages.
 
 ### Running Locally
-To deploy SQL Validator locally, follow these steps:
 1. Clone the repository: `git clone https://github.com/Edwinexd/sql-validator.git`
 2. Install dependencies: `npm install`
 3. Start the development server: `npm start`
 
+## Architecture
+### Oracle System
+The **oracle** (`data/oracle.json`) is the single source of truth for the database schema, canonical data, and all 110 reference SQL queries. It uses language-agnostic placeholders (e.g. `{{table:Person}}`, `{{col:Person.city}}`, `{{city:6}}`) that are resolved at generation time using a language pack.
+
+The oracle is encrypted (`data/oracle.enc`) before committing so students cannot see the answers.
+
+### Language Packs
+Language definitions live in `languages/` (e.g. `sv.ts`, `en.ts`). Each pack provides:
+- Localized names, addresses, cities, course names, room names
+- Per-person IDs, postal codes, phone numbers
+- Schema translations (table and column names)
+- 110 localized question descriptions
+- UI strings
+
+### Generation Pipeline
+The `generate-language.ts` script combines the oracle with a language pack to produce per-language output:
+1. Creates a SQLite database with localized schema and data
+2. Runs all reference queries to produce expected result sets
+3. Outputs `questionpool.json` and `data.sqlite3` into `public/languages/<code>/`
+
+The `generate-erd.ts` script produces light/dark SVG database diagrams from the generated databases.
+
+Both scripts support `--all` to auto-discover and process all languages.
+
+### Scripts
+| Script | Description |
+|---|---|
+| `npm run generate-all` | Regenerate all languages (question pools, databases, ERDs) |
+| `npm run generate-lang -- --lang <code> --plain` | Generate a single language using unencrypted oracle |
+| `npm run generate-lang -- --all --plain` | Generate all languages |
+| `npm run generate-erd -- --all` | Regenerate ERD diagrams for all languages |
+| `npm run encrypt-oracle -- <password>` | Encrypt `oracle.json` to `oracle.enc` |
+| `npm run decrypt-oracle -- <password>` | Decrypt `oracle.enc` to `oracle.json` |
+
+### Adding a New Language
+1. Create a new file in `languages/` (e.g. `de.ts`) implementing the `LanguageDefinition` interface
+2. Run `npm run generate-all`
+
 ## Screenshots
 ## Main Application
 <div style="display: flex; padding: 0;">

data/oracle.enc

@@ -50,7 +50,7 @@
     "decrypt-oracle": "tsx scripts/decrypt-oracle.ts",
     "encrypt-oracle": "tsx scripts/encrypt-oracle.ts",
     "generate-erd": "tsx scripts/generate-erd.ts",
-    "generate-all": "tsx scripts/generate-language.ts --lang sv --plain && tsx scripts/generate-erd.ts --db public/languages/sv/data.sqlite3 --out public/languages/sv && tsx scripts/generate-language.ts --lang en --plain && tsx scripts/generate-erd.ts --db public/languages/en/data.sqlite3 --out public/languages/en"
+    "generate-all": "tsx scripts/generate-language.ts --all --plain && tsx scripts/generate-erd.ts --all"
   },
   "eslintConfig": {
     "extends": [