IMX471 AIQB tuning forces AE to ISO 4096 in well-lit room

**Environment:** Sony IMX471 (SONY471A), Chicony CJFOE833 module, Lunar Lake IPU7X, ThinkPad X9-14 Gen 1, AIQB: IMX471_AAJH5-D_LNL.aiqb (IQStudio 24.40.2.0)

**Problem:** Auto-exposure converges at maximum gain in a normally lit room:
```
AE exp[0] ag 16.000000 dg 4.000000 Fn 2.400000 time 33334us iso 4096
AE Converged: YES, distance_convergence: -0.465956
```

Manual exposure at gain=18 (ISO 800) produces a properly exposed image. The AIQB tuning has incorrect sensor sensitivity calibration.

**Impact:** Produces extremely noisy video unusable for conferencing. Forces users to libcamera SoftISP to get working AE.

**Additional findings:**
- HAL NR (strength 20) has no visible effect at ISO 4096
- Increasing driver fll_def does not help — HAL tet limits cap at 33ms
- HAL CCM and color pipeline work correctly — only AE is broken