docs: fix unresolved and private intra-doc links (#78)

A full `cargo doc --workspace` (and docs.rs, which builds with
`-D rustdoc::all`) emitted five broken intra-doc links. docs.rs treats
these as hard errors, so any 0.2.x doc build was at risk of aborting.

- mama.rs: `[`Fama`]` -> `[`crate::Fama`]` (Fama lives in another module)
- standard_error.rs: `[`crate::Bollinger`]` -> `[`crate::BollingerBands`]`
  (the public type is `BollingerBands`, not `Bollinger`)
- aggregator.rs: drop the link to the private `OpenBar::into_candle`,
  keep it as plain code text
- resample.rs: drop the link to the private `RolledBar::into_candle`
- csv.rs: `CandleReader::with_timestamp_parser` never existed; reword to
  state plainly that ISO/RFC timestamps must be converted to integers

Verified with `RUSTDOCFLAGS="-D rustdoc::broken_intra_doc_links \
-D rustdoc::private_intra_doc_links" cargo doc --workspace --no-deps`:
clean, zero warnings.

crates/wickra-core/src/indicators/mama.rs

@@ -32,7 +32,7 @@ pub struct MamaOutput {
 /// + fama_prev * (1 - 0.5 * fast_limit)`, lagging MAMA so crossovers signal
 /// trend reversals.
 ///
-/// The indicator emits both lines as a [`MamaOutput`]. Use the [`Fama`] wrapper
+/// The indicator emits both lines as a [`MamaOutput`]. Use the [`crate::Fama`] wrapper
 /// in this module to expose just the slow line if needed (e.g. for chaining).
 ///
 /// # Example

crates/wickra-core/src/indicators/standard_error.rs

@@ -23,7 +23,7 @@ use crate::traits::Indicator;
 /// This is the textbook **standard error of estimate** of OLS: it measures
 /// the typical distance between the observed prices and the fitted line,
 /// using the residual degrees of freedom `n − 2`. It is the spread that
-/// drives [`crate::Bollinger`]-style bands around a regression instead of
+/// drives [`crate::BollingerBands`]-style bands around a regression instead of
 /// around an SMA — when the price hugs its trend, `StdErr` is small.
 ///
 /// Each `update` is O(1): the `Σx` and `Σxx` terms depend only on `period`