feat: load dynamic settings and add identity selection page

.github/prompts/3-dynamicdata.prompt.md

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+next step after "2-dateselect.prompt.md":
+
+i want to be able to define the available activities in a separate json file. for each activity, i want to define the following properties: name and icon. icon will always be a simple unicode icon. so it should be able to be treated as a character in the html
+
+for now, i want to drop the option to select a time. the date itself should be enough

.github/prompts/4-more-dynamicdata.prompt.md

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+now i want to be able to define available dates in the same file. call the file appsettings.json instead of activities.json. the file should contain two arrays: one for activities and one for available dates. each date should be defined as a string in the format "YYYY-MM-DD".
+
+additional to that, i want to be able to define names that can be selected for me to know who schedules the date. so the file should contain a third array called "names" with strings for each name. Add a page right after the date selection