chore: clean up release notes — remove stale DataFlow-era files

Remove 9 release notes files from the DataFlow→DataLinq rebranding that had
incorrect version numbers not matching any actual release:
- DataLinq.Net 1.0.2, 1.1.0, 1.2.0, 1.2.1 (actual latest: 1.0.0)
- DataLinq.Snowflake 1.0.2, 1.2.1, 1.3.0 (actual: 1.0.0→1.0.1→1.1.0→1.2.0)
- DataLinq.Spark 1.2.0, 1.2.1 (actual latest: 1.0.0)

Add DataLinq.Snowflake v1.2.0 release notes.
Rewrite CHANGELOG.md to reflect only actual released versions.

Author: improveTheWorld

releasenotes/CHANGELOG.md

@@ -1,31 +1,15 @@
-# DataLinq.NET Changelog
+# DataLinq Changelog
 
 > All notable changes to DataLinq packages are documented in this folder.
 
 ## Packages
 
-| Package | Latest | Changelog |
-|---------|--------|-----------|
-| **DataLinq.NET** | v1.2.1 | [v1.2.1](DataLinq.Net_1.2.1.md), [v1.2.0](DataLinq.Net_1.2.0.md), [v1.1.0](DataLinq.Net_1.1.0.md), [v1.0.2](DataLinq.Net_1.0.2.md) |
-| **DataLinq.Spark** | v1.2.1 | [v1.2.1](DataLinq.Spark_1.2.1.md), [v1.2.0](DataLinq.Spark_1.2.0.md) |
-| **DataLinq.Snowflake** | v1.1.0 | [v1.1.0](DataLinq.Snowflake_1.1.0.md), [v1.0.2](DataLinq.Snowflake_1.0.2.md) |
+| Package | Latest | Release Notes |
+|---------|--------|---------------|
+| **DataLinq.NET** | v1.0.0 | First release |
+| **DataLinq.Spark** | v1.0.0 | First release |
+| **DataLinq.Snowflake** | v1.2.0 | [v1.2.0](DataLinq.Snowflake_1.2.0.md), [v1.1.0](DataLinq.Snowflake_1.1.0.md) |
 
 ## Naming Convention
 
 Files follow: `{PackageName}_{Version}.md`
-
-## Quick Links
-
-### DataLinq.NET (OSS)
-- **v1.2.1** — YAML record support fix, ObjectMaterializer regressions, audit report 2 doc corrections
-- **v1.2.0** — RSA licensing, 60% coverage, test reorganization
-- **v1.1.0** — Cases pattern, ParallelAsyncQuery
-- **v1.0.2** — Bug fixes, stability
-
-### DataLinq.Spark (Enterprise)
-- **v1.2.1** — Bug fixes, nested object access
-- **v1.2.0** — Auto-UDF, Assembly Distribution
-
-### DataLinq.Snowflake (Enterprise)
-- **v1.1.0** — Auto-UDF, ForEach server-side iteration, Source Generator, entity-parameter decomposition, intelligent PascalCase↔snake_case naming, type-safe UpdateOnly, 11 bug fixes, 540 integration tests, obfuscated package
-- **v1.0.2** — 29 bug fixes: VARIANT columns, Cases multi-column, Join pre-filter, ForEach double-exec, window base columns, GroupBy/Join MemberInit, Distinct+Count, MergeTable upsert, SQL translator, IL2Java Math, obfuscation