chore(release): prepare Ack 1.7.0

[leoafarias]

Summary

Prepare the coordinated Ack 1.7.0 stable release across all five publishable packages:

• ack: 1.7.0
• ack_generator: 1.7.0 (depends on ack: ^1.7.0)
• ack_firebase_ai: 1.7.0
• ack_json_schema_builder: 1.7.0
• ack_mcp_dart: 1.7.0

Highlights in 1.7.0

• Unified @Schemable() & Annotations in ack: ack_annotations is retired; annotations now ship in package:ack/ack.dart, package:ack/annotations.dart, and package:ack/format_annotations.dart. @Schemable() drives both schema-first and class-first generation (@AckInfer() and @AckModel() are deprecated for 2.0.0).
• Convention-Based Schema Resolution & Typed copyWith: Class-first fields whose types declare a static schema getter or generic schema<A>() factory resolve automatically; schema-first models emit static final schema; and generated copyWith is now a typed $ClassCopyWith<Class> getter.
• Expanded JSON Schema Import (Ack.fromJsonSchema()): Adds multipleOf (exact decimal division), contains, if/then/else, built-in string and numeric format assertions, x-* vendor extensions, Draft-07 $schema URIs, ECMA-262 Unicode pattern mode, and JsonSchemaValidationError location diagnostics.
• Consolidated Changelogs & Docs: Consolidated all 1.7.0-beta.* entries into a single ## 1.7.0 release section across the root and package changelogs and updated installation/publishing version snippets to ^1.7.0.

Verification

• dart scripts/verify_release_tag.dart v1.7.0 --skip-ancestry (v1.7.0 is releasable.)
• dart scripts/publish_dry_run.dart (0 warnings across all 5 packages)