Fix 4 verified skill content bugs

[JoshDFN]

Summary

Fixes 4 confirmed issues from #1 (5 others were verified as false positives).

Verified and fixed:

• Issue 1: Added [package] + [lib] crate-type=["cdylib"] to 6 Rust Cargo.toml examples (https-outcalls, icrc-ledger, vetkd, stable-memory, wallet, internet-identity). Without this, cargo build produces an rlib, not a deployable .wasm.
• Issue 3: Replaced thread_local! heap storage with StableCell for OWNER in the Internet Identity Rust backend. Previous code lost ownership on canister upgrade, allowing anyone to reclaim via init_owner().
• Issue 4: Fixed SNS token distribution math — governance was 5,200,000 tokens but total declared 10,000,000. Reduced governance to 5,000,000 so allocations sum correctly.
• Issue 9: Standardized ic-stable-structures to 0.7 across multi-canister and stable-memory skills (was 0.6 in multi-canister, 0.7 in stable-memory).

Verified as false positives (no fix needed):

• Issue 2: Nat64 is a built-in Motoko primitive — no import needed for type annotations
• Issue 5: @dfinity/* deprecation claim unverified
• Issue 6: Skills consistently use icp.json
• Issue 7: GitHub URLs already fixed (repo is public)
• Issue 8: vetKD skill already warns about ic-vetkeys availability

Closes #1

Test plan

• Build passes (npm run build)
• Verify Cargo.toml examples in all 8 Rust skills have [lib] crate-type = ["cdylib"]
• Verify II Rust backend uses StableCell
• Verify SNS allocations sum to declared total
• Verify ic-stable-structures version consistent across skills