Summer cleanup: XLSX export, WIDM-style quiz UI, CSS fixes (#162)

* Add CLAUDE.md, replace Makefile with Justfile, remove .junie

- Add CLAUDE.md with project overview, commands, architecture, and domain entity docs
- Remove Makefile in favour of the existing Justfile
- Remove .junie/AGENTS.md (knowledge transferred to CLAUDE.md)
- Update .gitignore: drop .junie/ entries, add .claude/settings.local.json
- Minor doc fixes in config/reference.php (typo, type correction)

* Clean up templates and CSS

- season.html.twig: remove dead empty column, drop redundant flex-row
- tab_overview.html.twig: extract Twig macro for confirm modals, fix duplicate aria-labelledby IDs
- tab_result.html.twig: remove dead comment, replace inline widths with CSS classes, simplify nested row/col forms to d-flex gap-1
- backoffice.scss: add col-result-xs/sm/md column width classes
- quiz.scss: replace broken display:grid + justify-self:center with flexbox centering

* Implement quizToXlsx() export and add export button

- QuizSpreadsheetService: implement quizToXlsx() as the inverse of
  fillQuizFromArray() — writes quiz questions and answers to XLSX using
  the same column layout as the import template
- BackofficeController: add exportQuiz() action at GET /backoffice/quiz/{quiz}/export
- tab_overview.html.twig: add Export to XLSX button in Quick actions

* Add unit tests for QuizSpreadsheetService

7 tests covering generateTemplate(), quizToXlsx(), and xlsxToQuiz():
- valid XLSX output and MIME type
- template without example reimports as empty
- template example data survives a reimport
- round-trip (export → reimport) preserves questions, answers, and correct flags
- empty quiz exports and reimports cleanly
- invalid MIME type throws InvalidArgumentException
- question with no answers throws SpreadsheetDataException with error list

* Fix quiz page vertical centering regression

The CSS cleanup broke vertical centering: flex on body causes main to
stretch full-width; place-items:center on a grid body only centers
items within their auto-sized track (not the track within body).

Fix: move background/color to html (full-viewport grid that centers
body), give body height:100% + display:grid + align-content:center
(centers the content track within full-height body) + justify-self:center
(shrink-wraps body width). Matches production behavior exactly.

* Improve quiz page layouts: WIDM-style answers and responsive centering

- Add green square answer buttons styled after the TV show
- Two-column answer grid for 6+ answers, single column on mobile
- fit-content centering for question pages so block matches question width
- Narrow fixed-width centering for form pages (enter name, select season)

* Use HeaderUtils::makeDisposition() for safe Content-Disposition filename

* Fix quizToXlsx to support unlimited answers and add header count tests

- Replace hardcoded 6-column arrays with dynamic Coordinate arithmetic
- Write data rows first to determine max answer count, write headers last
- Replace try/catch ErrorException in fillQuizFromArray with array_key_exists
- Add data-provider test covering 2, 6, 7, and 10 answers
- Add cross-question max-header and 7-answer round-trip tests

* Fix Sass healthcheck

* Improve quiz layout: add fixed topbar, include navigation, and clean up unused elements

- Add `.quiz-topbar` with fixed positioning and spacing in `quiz.scss`
- Update `base.html.twig` to include `quiz/nav.html.twig` in a new `nav` block
- Remove unused "Manage Quiz" button from `select_season.html.twig`

* Refactor generateTemplate to reuse quizToXlsx and add second example question

- generateTemplate now builds an in-memory Quiz entity and delegates to
  quizToXlsx, eliminating duplicate spreadsheet-building logic
- Adds a second example question "Wie is de mol?" with 10 Dutch names
  (5 male, 5 female) to better illustrate the import format
- Updates tests to assert both example questions and adds a test for the
  blank-row halt behaviour in fillQuizFromArray (achieving 100% coverage)

* Move PHPUnit cache to /tmp to avoid writing into the mounted volume

* Update src/Service/QuizSpreadsheetService.php

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

config/reference.php

@@ -127,7 +127,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  * }
  * @psalm-type ServicesConfig = array{
  *     _defaults?: DefaultsType,
- *     _instanceof?: InstanceofType,
+ *     _instanceof?: array<class-string, InstanceofType>,
  *     ...<string, DefinitionType|AliasType|PrototypeType|StackType|ArgumentsType|null>
  * }
  * @psalm-type ExtensionType = array<string, mixed>
@@ -727,7 +727,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *             servicename?: scalar|Param|null, // Overrules dbname parameter if given and used as SERVICE_NAME or SID connection parameter for Oracle depending on the service parameter.
  *             sessionMode?: scalar|Param|null, // The session mode to use for the oci8 driver
  *             server?: scalar|Param|null, // The name of a running database server to connect to for SQL Anywhere.
- *             default_dbname?: scalar|Param|null, // Override the default database (postgres) to connect to for PostgreSQL connexion.
+ *             default_dbname?: scalar|Param|null, // Override the default database (postgres) to connect to for PostgreSQL connection.
  *             sslmode?: scalar|Param|null, // Determines whether or with what priority a SSL TCP/IP connection will be negotiated with the server for PostgreSQL.
  *             sslrootcert?: scalar|Param|null, // The name of a file containing SSL certificate authority (CA) certificate(s). If the file exists, the server's certificate will be verified to be signed by one of these authorities.
  *             sslcert?: scalar|Param|null, // The path to the SSL client certificate file for PostgreSQL.
@@ -773,7 +773,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *                 servicename?: scalar|Param|null, // Overrules dbname parameter if given and used as SERVICE_NAME or SID connection parameter for Oracle depending on the service parameter.
  *                 sessionMode?: scalar|Param|null, // The session mode to use for the oci8 driver
  *                 server?: scalar|Param|null, // The name of a running database server to connect to for SQL Anywhere.
- *                 default_dbname?: scalar|Param|null, // Override the default database (postgres) to connect to for PostgreSQL connexion.
+ *                 default_dbname?: scalar|Param|null, // Override the default database (postgres) to connect to for PostgreSQL connection.
  *                 sslmode?: scalar|Param|null, // Determines whether or with what priority a SSL TCP/IP connection will be negotiated with the server for PostgreSQL.
  *                 sslrootcert?: scalar|Param|null, // The name of a file containing SSL certificate authority (CA) certificate(s). If the file exists, the server's certificate will be verified to be signed by one of these authorities.
  *                 sslcert?: scalar|Param|null, // The path to the SSL client certificate file for PostgreSQL.
@@ -852,7 +852,7 @@ use Symfony\Component\Config\Loader\ParamConfigurator as Param;
  *                     lock_path?: scalar|Param|null, // Default: "%kernel.cache_dir%/doctrine/orm/slc/filelock"
  *                     lock_lifetime?: scalar|Param|null, // Default: 60
  *                     type?: scalar|Param|null, // Default: "default"
- *                     lifetime?: scalar|Param|null, // Default: 0
+ *                     lifetime?: scalar|Param|null, // Default: null
  *                     service?: scalar|Param|null,
  *                     name?: scalar|Param|null,
  *                 }>,