v0.6.0-rc6

TollGate v0.6.0-rc6

Target-qualified release asset names (Option A): every published asset is now
tollgate-wrt_<ver>_<arch>-<target>.<ext> (and the offline bundle
tollgate-wrt-<ver>-<arch>-<target>-offline.tar.gz). This lets mips_24kc ship
BOTH ath79-generic and ath79-nand at once -- the two collided on one arch-only
name, which is why the NAND row was parked.

Matrix widened to 8 arch/target pairs: aarch64_cortex-a53/mediatek-filogic,
mips_24kc/ath79-generic, mips_24kc/ath79-nand,
aarch64_cortex-a72/bcm27xx-bcm2711, arm_cortex-a7/bcm27xx-bcm2709,
mipsel_24kc/mt7621, mips64_octeonplus/octeon-generic, x86_64/x86-64 -- each in
apk (25.12) and ipk (24.10) form, and each apk-lane arch with a WAN-less offline
bundle. aarch64_generic/armsr-armv8 stays parked (Gate K's restore-path
sentinel; not a club device).

Combines PR #84 (widening) and PR #85 (target-qualified naming); ships with the
installer's matching feedAssetURL(arch, target, ext) change
(OpenTollGate/tollgate-installer #143), without which every fresh deploy would
404 on the new names.

Module pin unchanged at cf7cad34 (PKG_SOURCE_TAG v0.6.0-rc4). PKG_VERSION
0.6.0_rc6.

Fixups after the first tag attempt (run 38776166350 failed 2 of 8 bundle jobs):
mipsel_24kc target mt7621 -> ramips-mt7621 (full hyphenated target path), and
arm_cortex-a7 -> arm_cortex-a7_neon-vfpv4 (bcm2709's actual package arch).
Both rows inherited from the widening; the bundle jobs only run on the tag.