fix(ui): add contextual keyboard status hint

[saurabhhhcodes]

What changed

• Added a contextual keyboard help hint to the permanent bottom status bar in src/ui/draw.rs.
• The normal status line now shows the primary app shortcuts for help, search, and quit while preserving the selected-count and package-manager indicators.
• Search mode and settings edit mode show mode-specific guidance so the bottom bar remains useful while the user is typing or editing.

Why

Issue #53 asks for a persistent keyboard help hint in the status bar. This keeps the most important shortcuts visible without adding a modal, changing the layout structure, or touching package-manager logic.

Fixes #53

How it was tested

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings -A dead_code -A clippy::type_complexity
• cargo test --workspace --all-targets --all-features
• cargo run -- --help
• Runtime TUI smoke check with cargo run, then quit with q
• GitHub CI Verify passed
• GitHub CI Build passed

UI evidence

Runtime TUI capture after cargo run:

The bottom bar now renders:

NORMAL  | Selected: 0  | Manager: Homebrew (macOS/Linux)  | Press '?' for help  •  'e' to search  •  'q' to quit

Scope checklist

• One issue only.
• One file changed: src/ui/draw.rs.
• No unrelated formatting or package-manager changes.
• PR targets the required dev branch.

[vercel]

Someone is attempting to deploy a commit to the pie's projects Team on Vercel.

A member of the Team first needs to authorize it.

[saurabhhhcodes]

Thanks for the guidance on the previous PR. I reopened this as a fresh PR against dev and expanded the description with the required what/why/testing/UI-evidence details.

Current status:

• GitHub CI Verify passed
• GitHub CI Build passed
• Remaining Vercel status is the external team authorization preview, not a code failure

If accepted, could you please add the scoring labels from the issue: gssoc:approved, level:beginner, and type:ui?

[pie-314]

@saurabhhhcodes you need to present screenshots wherever applicable, go through docs

[saurabhhhcodes]

Thanks, noted. I went through CONTRIBUTING.md, installed the Rust toolchain locally, and added runtime UI evidence to the PR body.

Updated verification:

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings -A dead_code -A clippy::type_complexity
• cargo test --workspace --all-targets --all-features
• cargo run -- --help
• runtime TUI smoke check with cargo run, then quit via q

Runtime status-bar evidence is now included in the PR body, showing the bottom hint: Press '?' for help • 'e' to search • 'q' to quit.