chore: license AGPL-3.0, zero clippy warnings, CHANGELOG through v1.6.0

License:
- Replace MIT/Apache-2.0 with AGPL-3.0-only across all crates and npm packages
- Replace LICENSE file with official GNU AGPL-3.0 text
- Remove LICENSE-MIT and LICENSE-APACHE

Code quality:
- Fix all 44 clippy warnings (zero remaining)
- Collapsible if statements, redundant closures, manual Option::map
- Remove duplicate #[allow(dead_code)] attributes in deprecated tool modules
- Add Default impl for CognitiveEngine
- Replace manual sort_by with sort_by_key

Documentation:
- Update CHANGELOG with v1.2.0, v1.3.0, v1.5.0, v1.6.0 entries
- Update README with v1.6.0 highlights and accurate stats (52K lines, 1100+ tests)
- Add fastembed-rs/ to .gitignore
- Add fastembed-rs to workspace exclude

1115 tests passing, zero warnings, RUSTFLAGS="-Dwarnings" clean.

packages/vestige-init/package.json

@@ -20,7 +20,7 @@
     "installer"
   ],
   "author": "Sam Valladares",
-  "license": "MIT",
+  "license": "AGPL-3.0-only",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/samvallad33/vestige.git",