bug(rrm): BaseConceptualModel signatures mismatch HBV implementations

[MAfarrag]

Context

PR review of #149 found that the abstract base class
`BaseConceptualModel` defines method signatures that don't match the
concrete `HBV` and `HBVBergestrom92` implementations. This causes
`# type: ignore[override]` suppressions throughout and makes the
base class contract misleading.

Related: #140, #142, #145

Problem / Current Behaviour

Signature mismatches

Method	Base class	HBV	Issue
`precipitation`	Missing `prec` param, has unused `pcorr`	Has `prec`, no `pcorr`	Param mismatch
`snow`	`(temp, ttm, cfmax, ...)`	`(cfmax, temp, ttm, ...)`	Param order swapped
`response`	Returns `tuple[float, float, float]`	Returns 4-tuple	Return arity mismatch
`simulate`	`(prec, temp, et, ll_temp, par, ...)`	`(prec, temp, et, par, init_st, ll_temp, ...)`	Param order swapped
`soil`	Docstring uses `infiltration`	HBV uses `inf`	Param name mismatch

Affected locations

File	Symbol	Notes
`src/Hapi/rrm/base_model.py`	`BaseConceptualModel`	All 6 abstract methods
`src/Hapi/rrm/hbv.py`	`HBV`	All overridden methods
`src/Hapi/rrm/hbv_bergestrom92.py`	`HBVBergestrom92`	All overridden methods

Proposed Solution

Align the base class signatures with the actual HBV implementation
(which is the only actively used variant), or make the base class
use `*args, **kwargs` with documentation of the expected interface.

Out of Scope

• Refactoring HBV variants into a shared base (Refactor HBV variants to use BaseHBVModel #142, Deduplicate hydrological routines across HBV variants #145)
• Adding `@abstractmethod` decorators (intentionally removed)

Effort Estimate

Size: `M`
Rationale: Requires careful alignment of 6 method signatures
across 3 files without breaking existing callers.

Definition of Done

• All base class method signatures match HBV implementations
• `# type: ignore[override]` comments removed from HBV/HBVBergestrom92
• Docstring parameter names match actual function signatures
• `response` return type annotation is 4-tuple
• mypy passes without override suppressions for these methods
• Existing tests pass

[MAfarrag]

Closed: created in error. These are follow-up items from PR #152 review, not standalone issues.