Add desktop env vault for applying values to .env.example templates

[Evenss]

Description

Add a desktop env management tool that stores environment variables as reusable key-value records and can apply them to a target project's .env.example template to generate a .env file.

This feature should be generic and not tightly coupled to ContextSeek. ContextSeek's own .env.example can be used as the initial seed/template, but the underlying capability should be reusable for other projects.

Requirements:

• Store env values as reusable KV records in a project-local env vault.
• Encrypt the vault file on disk.
• For the MVP, use an application-level fixed encryption key so users do not need to enter a passphrase or unlock the vault manually.
• Use .env.example as the template/schema when applying env values to a project.
• Create a .env file that follows the keys from .env.example.
• For each key in .env.example, automatically fill the value if the key exists in the Env Manager KV store.
• If a key has no matching value, show a prompt/dialog for the user to fill it manually.
• After the user fills missing values, write the generated .env file.
• Sync newly filled or updated values back into the Env Manager KV store.
• Secret-like values should be hidden by default in the UI.
• Users can click to show or hide each secret value.
• MVP only needs to support one .env.example → .env flow per project.

Out of scope for MVP:

• Preserving original .env comments, blank lines, or formatting.
• Managing multiple env files such as .env.local, .env.dev, or .env.prod.
• Strong local security through user passphrases or OS keychain integration.
• Complex variable expansion such as FOO=${BAR}.

Acceptance criteria:

• A desktop Env management view is available.
• The view can initialize seed keys from ContextSeek's .env.example.
• The view can select/read a target project's .env.example.
• The tool generates a .env file using keys from .env.example.
• Matching keys are populated from the Env Manager KV store.
• Missing keys are collected from the user through a dialog.
• Newly entered values are synced back into the Env Manager KV store.
• Env values are stored in an encrypted project-local vault file.
• No user passphrase or manual unlock step is required for the MVP.