Clean up formatting and add change password to accounts page

[AdrianDAlessandro]

Description

A couple of changes I noticed were required when reviewing #617 (this currently merges into that branch)

Explained:

• Adding bg-secondary back to the account pages, which was inadvertently removed when making it extend base.html
• The password change form should be in the accounts page, so I have changed the base form for that and updated the highlight condition so it it clear which page you're on.

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Technical work (non-breaking, change which is work as part of a new feature)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass (eg. python -m pytest)
• The documentation builds and looks OK (eg. mkdocs serve)
• Pre-commit hooks run successfully (eg. pre-commit run --all-files)

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Sahil590]

LGTM