docs: add license rationale, Python/PineScript guides, API updates

- Add docs/license.md with Apache 2.0 rationale and patent protection analysis
- Add docs/python.md and docs/pinescript.md platform guides
- Expand README license section with disclosure and link to rationale
- Update docs/api.md and docs/architecture.md
- Update Python bindings: helpers, all indicator modules, pyproject.toml
- Add Python tests for Arrow and Polars integration
- Update TValue core type and documentation
- Add fix_length_to_period tooling script

lib/core/tvalue/tvalue.cs

@@ -26,6 +26,13 @@ public readonly record struct TValue(long Time, double Value) : ISpanFormattable
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static implicit operator DateTime(TValue tv) => new(tv.Time, DateTimeKind.Utc);
 
+    /// <summary>
+    /// Implicitly converts a raw double to a TValue with DateTime.UtcNow timestamp.
+    /// Enables ergonomic APIs like <c>sma.Update(110.4)</c>.
+    /// </summary>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static implicit operator TValue(double value) => new(DateTime.UtcNow, value);
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public override string ToString()
     {