Albums: Preload more items for auto-completion in "Add to album" dialog

[ppprism]

This is a small hotfix to the "Add photos to album" dialog.

If there are more than 1000 albums in photoprism, a problem arises in the user interface:

• you cannot add photos to existing albums that are not included in the range
• worse, it looks like there is no such album yet, leading to duplicate albums with same name when pressing add button

This pull requests increases the max album fetch count to 10000 as quickfix and removes the magic number, declaring MAX_COUNT as explicit constant.

Future improvements of REST API may one of the following:

• include an "infinite count" flag, as the intention is always to provide all albums in autocomplete dialog
• make count query parameter optional

Background:
I have a bunch of auto-generated albums (> 1000) from external sources and found it very confusing, that only one half of albums have been displayed in the autocomplete.

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Acceptance Criteria:

• Features and improvements are fully implemented so that they can be released at any time without additional work

This is a small change (projects with < 1000 albums not affected in any way), hence following points are neglected:

• Automated unit and/or acceptance tests have been added to ensure the changes work as expected and to reduce repetitive manual work
• User interface changes are fully responsive and have been tested on all major browsers and various devices
• Database-related changes are compatible with SQLite and MariaDB
• Translations have been / will be updated (specify if needed)
• Documentation has been / will be updated (specify if needed)
• Contributor License Agreement (CLA) has been signed

[CLAassistant]

All committers have signed the CLA.

[lastzero]

Thanks! Apparently we didn't expect private users to have more than 1000 albums when implementing this...