fix: handle Room 3 empty queries and improve release obfuscation

[SeniorZhai]

Opening a bot profile can crash when its creator is not cached: Room 3 throws for the empty LiveData<User> query before the existing null-triggered refresh runs. Make 12 single-row observation queries nullable across user, conversation, circle, address, asset/token, and sticker DAOs. Propagate the types through their callers and let sticker preview wait for a missing sticker to load.

Review of generated empty-result checks in 70 DAO implementations found no further equivalent optional-row queries. Aggregate wallet summaries and the required local encryption identity retain their non-null contracts.

Also narrow R8 keep rules for annotated API fields and non-public Kotlin runtime classes while retaining persisted serialization models, JobQueue jobs, unannotated JSON fields, enums, throwables, and reflected coroutine stack-trace labels.

Measured from the final Google Play release AAB's BUNDLE-METADATA/com.android.tools/r8.json, against master 464502fa05 with the same toolchain:

Metric	Before	After	Change
Obfuscation	49.65%	53.14%	+3.49 percentage points
Optimization	54.18%	53.07%	-1.11 percentage points
Shrinking	56.58%	60.25%	+3.67 percentage points

Obfuscation improved by approximately 7.0% relative to baseline. DEX size decreased from 48,292,016 to 46,529,760 bytes.

Validation:

• Final Google Play release AAB and APK builds completed, including lintVital tasks. Existing third-party SDK warnings remain; mapping upload tasks were excluded.
• Three targeted JVM tests passed. The database test covers all 12 missing-row queries; each newly fixed query reproduced the corresponding Room exception before its fix.
• Local post-R8 JVM smoke checks covered JSON round trips, baseline-to-current Java deserialization, enums, coroutine resumption, and reflected stack-trace labels.
• Device release checks covered wallet assets/transaction details, crypto/perpetual lists and details, charts, market search, chat/App Card rendering, settings, and appearance. The bot-profile crash was reproduced, then retested successfully after the user-query fix, together with shared-media empty states and background/foreground return.

The subsequent 10-query sweep passed JVM tests and the final release build; a periodic device PIN reminder prevented repeating the full UI pass for that sweep. Actual transfers/trades, PIN/signing, and historical media restoration were not exercised. Push registration remains unverified because the local Firebase configuration was rejected.