feat: hle_fallback on 39 emulator profiles (266 entries)

Batch analysis of all 273 profiles to identify HLE/embedded
fallbacks. Added hle_fallback: true where the core has verified
software replacement for missing BIOS files:

- Embedded ROMs: vice (102), ep128emu (22), fuse (18), frodo (4)
- HLE BIOS: bsnes* (33 across 3 profiles), puae (9 AROS),
  noods (4), melonds* (6 FreeBIOS), flycast (3 reios)
- Open-source replacements: sameboy (8), pokemini (1), gpsp (1)
- Built-in fallbacks: np2kai (7), atari800 (6 Altirra),
  picodrive (3), quasi88 (4), gambatte (2)

Conservative: only added where notes or source code confirm HLE.
Skipped 50+ profiles where files are optional alternatives, not
HLE replaceable (neocd, opera, kronos, pcem, etc.)

emulators/melonds_ds.yml

@@ -27,16 +27,19 @@ files:
   - name: bios7.bin
     system: nintendo-ds
     required: false
+    hle_fallback: true
     md5: df692a80a5b1bc90728bc3dfc76cd948
     note: "NDS ARM7 BIOS"
   - name: bios9.bin
     system: nintendo-ds
     required: false
+    hle_fallback: true
     md5: a392174eb3e572fed6447e956bde4b25
     note: "NDS ARM9 BIOS"
   - name: firmware.bin
     system: nintendo-ds
     required: false
+    hle_fallback: true
     sha1: 8497afdd16af92d6887b71582846c40514e9039f
     md5: 145eaef5bd3037cbc247c213bb3da1b3
     size: 262144