Env var list should show one row per variable, not one row per unique value

Currently, the env var list collapses or splits rows based on whether the value is identical across environments:

Same value in dev + prod -> one row
Different values -> two rows

This breaks the core mental model. The number of rows in the list no longer equals the number of variables. Scanning becomes unreliable because you can't tell at a glance how many variables you have or whether a variable exists in a given environment.

Proposed behavior:

Always show one row per variable name
Clicking a row opens a modal
The modal shows each environment with its current (masked) value and an input to update it
All edits to one variable happen in one place

This keeps the list scannable and predictable. The "collapse identical values" optimization can still happen inside the modal if space is a concern, but it shouldn't affect the list itself.

Currently, the env var list collapses or splits rows based on whether the value is identical across environments:

Same value in dev + prod -> one row
Different values -> two rows

Proposed behavior:

Always show one row per variable name
Clicking a row opens a modal
The modal shows each environment with its current (masked) value and an input to update it
All edits to one variable happen in one place

This keeps the list scannable and predictable. The "collapse identical values" optimization can still happen inside the modal if space is a concern, but it shouldn't affect the list itself.