build(release): bump 6.1.8 -> 6.1.9 for staking-selfheal fix

Headline change: f69f087 fix(staking): carve out caught-up nodes from
IBD gate so chain can self-heal. Closes the v6.1.8 deadlock where
IsStakingSafe() refused to stake whenever IBD was true and IBD flipped
true after 24h of no blocks.

Also includes the secondary commits since v6.1.7:
- 41e3898 + 64556dc: CLI flag handling
- 7a71904 (already in v6.1.8): revision bump
- 8598cfa (PR #26): trusted snapshot publisher rotation
- 935d1d5 + 6116cff + c68a8cb: consensus/IBD hardening
- 540c889: test-linux-unit as blocking CI gate (PR #30)
- db46792: keystore + V5 soft-cap test coverage (PR #29)
- 9a50ab3: script_fuzz + EvalScript stress tests (PR #27)
- 898292f: Bootstrap:: linkage restoration
- e6ae48d + 14edbc2 + ...: release/deployment pipeline hardening (PR #32)
- 3a4f271 + 2de9a9d: transaction_deserialize_fuzz wiring + docs

The CHANGELOG notes v6.1.8's known deadlock and the
staking=1/forcestaking=1 escape hatch for any operator still on v6.1.8.

Codex verdict: see the underlying B-grade commits f69f087 and 3a4f271.

src/clientversion.h

@@ -8,7 +8,7 @@
 // These need to be macros, as version.cpp's and triangles-qt.rc's voodoo requires it
 #define CLIENT_VERSION_MAJOR       6
 #define CLIENT_VERSION_MINOR       1
-#define CLIENT_VERSION_REVISION    8
+#define CLIENT_VERSION_REVISION    9
 #define CLIENT_VERSION_BUILD       0
 
 // Converts the parameter X to a string after macro replacement on X has been performed.