feat: improve ui for exercises and support cardio and isometric types

[Sim-sat]

Description

Description

What problem does this PR solve?

1. Redundant column headers rendered above every individual set.
2. No support isometric exercises (which measure holds instead of reps).
3. No dedicated interface existed for cardio exercises, forcing them into a set-based format that doesn't make sense.
4. The edit and log exercise dialogs were overloaded with inputs optimized exclusively for strength training.
5. Drag and drop functionality was broken due to unstable array index keys.

How did you implement the solution?

1. Created a standalone header component rendered once per exercise. Reduced the size of the weight input and set action buttons to display only on hover.
2. Added an "isometric" exercise type that visually swaps "Reps" for "Hold (s)" on the frontend. Note: Since the backend does not natively support isometric holds, this value is still saved as reps.
3. Built a new, dedicated cardio component from scratch to display only relevant metrics without a set structure.
4. Relocated secondary input fields into a collapsible advanced section to clean up the default view.
5. Implemented stable, unique identifiers (crypto.randomUUID()) for drag-and-drop element keys.

I also added the option to style the input element for the UnitInput component which was missing. We could think about adding a few more variations depending on the type in the future.

Linked Issue: #

How to Test

1. Check out this branch and run ...
2. Navigate to...
3. Verify that...

PR Type

• Issue (bug fix)
• New Feature
• Refactor
• Documentation

Checklist

All PRs:

• [MANDATORY - ALL] Integrity & License: I certify this is my own work, free of malicious code, and I agree to the License terms.

New features only:

• [MANDATORY for new feature] Alignment: I have raised a GitHub issue and it was reviewed/approved by maintainers or it was approved on Discord.

Frontend changes (SparkyFitnessFrontend/ or src/):

• [MANDATORY for Frontend changes] Quality: I have run pnpm run validate and it passes.
• [MANDATORY for Frontend changes] Translations: I have only updated the English (en) translation file.

Backend changes (SparkyFitnessServer/):

• [MANDATORY for Backend changes] Code Quality: I have run typecheck, lint, and tests. New files use TypeScript, new endpoints have Zod schemas, and new endpoints include tests.
• [MANDATORY for Backend changes] Database Security: I have updated rls_policies.sql for any new user-specific tables.

UI changes (components, screens, pages):

• [MANDATORY for UI changes] Screenshots: I have attached Before/After screenshots below.

Screenshots

Exercise Entries

Isometric (Extended Advanced Section)	Cardio (Collapsed Advanced Section)

Workout Preset

Before	After

Colored Types

[gemini-code-assist]

Code Review

This pull request significantly refactors the exercise logging system to support cardio and isometric exercise categories, introducing new components like CardioLog and SetHeader for specialized layouts. It also improves the drag-and-drop experience by transitioning to unique set identifiers (_dndId). Feedback focuses on a critical bug in the set duplication logic that causes ID collisions and provides suggestions to prevent 'undefined' strings from appearing in CSS classes when using the new optional inputClassName prop in UnitInput.