release: stabilize fojin-cli v0.3.0

[xr843]

Summary

• prepare the 0.3.0 release line and raise the MSRV to Rust 1.95
• upgrade bundled SQLite to 3.53.2, make short queries literal, and deterministically deduplicate parallel results
• harden release archives, checksums, immutable Actions, permissions, dry runs, and duplicate-release protection
• make the installer fail closed unless the matching release archive checksum is present and valid
• document the transition and add security, contribution, issue, and pull-request guidance

Verification

• cargo +1.95.0 fmt --all -- --check
• cargo +1.95.0 clippy --all-targets --locked -- -D warnings
• cargo +1.95.0 test --all --locked (100 passed)
• cargo +1.95.0 build --release --locked
• cargo +1.95.0 package --locked
• python3 -m pytest data-pipeline/tests -q (1 passed)
• bash tests/release-scripts.sh
• bash tests/install-script.sh
• ShellCheck 0.10.0 over installer, release, and test shell scripts
• actionlint 1.7.7 over both workflows
• final independent branch review: ready to merge, no Critical/Important findings

Release scope

This PR does not create a Git tag, GitHub Release, or crates.io publication. Those remain separate, explicit release actions after the merged release line is accepted.