feat(crowdfund): implement early‑bird discount & time‑based pricing

[martinshub-tech]

this pr closes #332

Description

Implements early‑bird discount and time‑based pricing for the crowdfunding contract.

Changes

• Added new DataKey entries to store discount windows and pricing tiers (see types.rs).
• Created/updated component components/early_bird.rs with role‑based checks and discount logic.
• Extended ShadeTrait with:
  • set_early_bird_params
  • apply_time_based_pricing
• Emitted new events: EarlyBirdDiscountApplied, TimeBasedPriceUpdated.
• Updated unit tests to cover the new pricing scenarios.

Verification

• cargo test -p crowdfund passes on Windows (GNU toolchain) and Linux CI.
• cargo clippy reports no warnings.
• Manual simulation verifies correct discount application.

Checklist

• Code compiles (cargo check).
• All tests pass.
• Documentation updated where applicable.

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