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-data/src/resample.rs

@@ -114,7 +114,7 @@ impl Resampler {
     ///
     /// # Errors
     /// Returns an error if the open bar's accumulated volume is non-finite
-    /// (see [`RolledBar::into_candle`]).
+    /// (see the internal `RolledBar::into_candle`).
     pub fn flush(&mut self) -> Result<Option<Candle>> {
         self.open.take().map(RolledBar::into_candle).transpose()
     }