chore: remove abandoned modular-architecture crates and dead contract modules

[RUKAYAT-CODER]

Summary

• Removes the 7 orphaned contracts/{insurance,licenses,market,marketplace,tokenization,governance,collaboration} crates. These are leftovers from a reverted modular-architecture experiment (376ae87, reverted in 76a8cac): none are Cargo workspace members, none are referenced anywhere, none are documented in CHANGELOG/TRACKING. Some (marketplace, tokenization, market) are written against the ink!/Substrate framework, not Soroban. contracts/market/src/lib.rs was a byte-identical copy of contracts/insurance/src/lib.rs.
• Removes notification_events.rs and notification_events_simple.rs from teachlink - superseded drafts; lib.rs only ever compiled notification_events_basic.
• Removes 10 more teachlink modules that were // mod'd out behind TODO: Fix ... compilation errors (pre-existing issue) comments with no tracked plan: collaboration, content_nft, content_quality, fractional, learning_paths, licensing, marketplace, royalty, social_events, social_learning. Checked open issues for each by name - zero matches. Left event_tests.rs / validation_tests.rs alone since those are disabled tests for currently-active modules (events, bridge, escrow, validation, etc.), not dead feature code, and left notification_tests.rs.disabled alone since TRACKING.md already tracks re-enabling it.
• Dedupes the pub use types::{...} re-export block in lib.rs, which repeated ~55 of its ~100 identifiers twice within the same use statement.
• Removes the unused testing/{performance,quality,analytics,security} scaffolding - confirmed via testing/Cargo.toml/testing/src/lib.rs that none of it is compiled; it duplicates the live scripts/*.sh + regression.yml gas/perf checks without ever being invoked.
• Adds a check-added-large-files pre-commit hook so build artifacts can't be committed again.

No workspace members changed (only contracts/teachlink and contracts/documentation ever were), so this shouldn't affect build/test behavior beyond the removed modules no longer existing.

Test plan

• cargo build --workspace
• cargo test --workspace --lib
• cargo clippy --workspace --all-features -- -D warnings
• CI (ci.yml, regression.yml) green

[RUKAYAT-CODER]

Note on CI: the Code Quality & Format Checks job's clippy step is failing here, but it's a pre-existing issue, not something introduced by this PR. cargo fmt --check was already failing on main before this PR (confirmed on the latest main run: https://github.com/rinafcode/teachLink_contract/actions/runs/25311283087), which meant the clippy step after it never actually got to run in CI. This PR fixes the formatting, which unblocked clippy for the first time and surfaced real, pre-existing compile errors in feature_flags.rs, validation.rs, and score.rs (duplicate MAX_OPERATIONAL_TIMEOUT/MAX_TIME_SKEW consts, duplicate ScoreError/ScoreResult definitions, references to nonexistent BridgeError variants, and calls to nonexistent soroban-sdk methods). None of that is touched by this cleanup. Tracking the fix separately since it needs its own review.