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/csv.rs

@@ -24,8 +24,9 @@ const REQUIRED_COLUMNS: [&str; 6] = ["timestamp", "open", "high", "low", "close"
 
 /// Default OHLCV CSV row layout.
 ///
-/// The timestamp is parsed as an `i64`; if your file ships an RFC3339 / ISO8601
-/// string instead, use [`CandleReader::with_timestamp_parser`].
+/// The timestamp is parsed as an `i64` (for example a Unix epoch). RFC3339 /
+/// ISO8601 string timestamps are not handled by this layout; convert them to
+/// integers before reading.
 #[derive(Debug, Clone, Deserialize)]
 pub struct DefaultRow {
     pub timestamp: i64,