Fast patching via IL rewriting of Bitwarden images (#278)

* Fast patching via IL rewriting of Bitwarden images

Brings back the pre-047c4dd approach of patching pre-built Bitwarden
images instead of cloning and building from source. The fast patch mode
(now default) pulls ghcr.io/bitwarden/{api,identity} and rewrites
Core.dll in-place using Mono.Cecil, bypassing the full source build.

Updated to work with current Bitwarden:
- Uses SingleFileExtractor.Core to extract Core.dll from the
  PublishSingleFile bundle before patching; replaces the native
  launcher with a shell script wrapper (exec dotnet /app/Api.dll)
  so entrypoint.sh continues to work unchanged
- LicensingService search is now namespace-agnostic (handles the
  Bit.Core.Services → Bit.Core.Billing.Services rename)
- Thumbprint matching uses Contains() instead of Equals() to handle
  the hidden Unicode LRM character prepended to the production
  thumbprint string literal in the compiled IL

The original source-build path is preserved and accessible via
BITBETTER_BUILD_FROM_SOURCE=1.

Signed-off-by: Lorenzo Moscati <lorenzo@moscati.page>

* Address review: fix correctness and robustness

- dotnet publish -c Release with explicit -o to match Dockerfile expectation
- Add --platform "$TARGETPLATFORM" to fast-patch docker builds for parity with source-build mode
- mkdir -p for idempotent .keys directory creation
- Align namespace to BitwardenSelfLicensor (repo convention)
- Branch bundle extraction on .dll extension instead of bare catch; exit 1 with clear message on failure
- Replace First() with FirstOrDefault() + targeted error on missing licensing resource
- FixRuntimeConfig derives framework name/version from includedFrameworks; switch to LatestPatch rollForward

Signed-off-by: Lorenzo Moscati <lorenzo@moscati.page>

* Add BITBETTER_BUILD_FROM_SOURCE notes to README.md

Signed-off-by: Lorenzo Moscati <lorenzo@moscati.page>

---------

Signed-off-by: Lorenzo Moscati <lorenzo@moscati.page>
Co-authored-by: h44z <christoph.h@sprinternet.at>

src/bitBetter/Dockerfile

@@ -0,0 +1,13 @@
+ARG BITWARDEN_TAG
+FROM ${BITWARDEN_TAG}
+
+COPY bin/Release/net8.0/publish/* /bitBetter/
+COPY ./.keys/cert.cert /newLicensing.cer
+
+RUN set -e; set -x; \
+    if [ -f /app/Api ]; then EXEC=Api; else EXEC=Identity; fi && \
+    dotnet /bitBetter/bitBetter.dll /newLicensing.cer /app/$EXEC && \
+    rm -f /app/$EXEC && \
+    printf '#!/bin/sh\nexec dotnet /app/%s.dll "$@"\n' "$EXEC" > /app/$EXEC && \
+    chmod +x /app/$EXEC && \
+    rm -rf /bitBetter /newLicensing.cer